Merge branch 'master' into debian

15 files changed, 986 insertions, 30 deletions

diff --git a/Changelog b/Changelog
index f0c9e50..4a18c52 100644
--- a/Changelog
+++ b/Changelog
@@ -105,6 +105,10 @@ interimap (0.5) upstream;
  - interimap: for the reason explained above, limit number of messages
    to 128 per APPEND command (only on servers advertizing MULTIAPPEND,
    for other servers the number remains 1).
+ - interimap: gracefully ignore messages with a NIL RFC822 attribute.
+ - pullimap: treat messages with a NIL RFC822 attribute as empty.
+ - pullimap: fix mangling of data lines starting with a dot (when an RFC
+   5322 line starts with a '.', double it).
 
  -- Guilhem Moulin <guilhem@fripost.org>  Fri, 10 May 2019 00:58:14 +0200
 
diff --git a/benchmark/dovecot.conf b/benchmark/dovecot.conf
new file mode 100644
index 0000000..55301d9
--- /dev/null
+++ b/benchmark/dovecot.conf
@@ -0,0 +1,55 @@
+log_path = /dev/shm/mail.log
+mail_home = /dev/shm/vmail/%u
+mail_location = mdbox:~/mail
+ssl = no
+
+listen = 127.0.0.1
+namespace {
+    inbox = yes
+    separator = /
+}
+
+# https://wiki.dovecot.org/HowTo/Rootless
+base_dir = /dev/shm/dovecot/run
+default_internal_user  = nobody
+default_internal_group = nogroup
+default_login_user     = nobody
+
+service anvil {
+    chroot =
+}
+service imap-login {
+    chroot =
+}
+service stats {
+    chroot =
+}
+
+passdb {
+    args = scheme=PLAIN username_format=%u /dev/shm/dovecot/users
+    driver = passwd-file
+}
+userdb {
+    args = username_format=%u /dev/shm/dovecot/users
+    driver = passwd-file
+}
+
+protocols = imap
+
+mail_plugins = zlib
+protocol imap {
+    mail_plugins = imap_zlib
+}
+
+service imap-login {
+    inet_listener imap {
+        # disable
+        port = 0
+    }
+    inet_listener interimap {
+        port = 10143
+    }
+    inet_listener offlineimap {
+        port = 10144
+    }
+}
diff --git a/benchmark/random_maildir.pl b/benchmark/random_maildir.pl
new file mode 100755
index 0000000..363eb41
--- /dev/null
+++ b/benchmark/random_maildir.pl
@@ -0,0 +1,57 @@
+#!/usr/bin/perl
+
+#----------------------------------------------------------------------
+# Generate a random mbox
+# Copyright © 2019 Guilhem Moulin <guilhem@fripost.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#----------------------------------------------------------------------
+
+use warnings;
+use strict;
+
+use Time::HiRes ();
+use POSIX qw{strftime setlocale};
+use Crypt::URandom "urandom";
+
+setlocale(POSIX::LC_TIME, "C");
+
+foreach (qw/cur new tmp/) {
+    my $d = $ARGV[0] ."/". $_;
+    mkdir $d, 0700 or die "mkdir: $!"
+}
+
+my $NEW = $ARGV[0] ."/new";
+for (my $i = 0; $i < $ARGV[1]; $i++) {
+    my $timestamp = Time::HiRes::gettimeofday();
+    my $filename = sprintf("%10d.M%010d.localhost", $timestamp, $i);
+    open my $out, ">", $NEW ."/". $filename or die "open: $!";
+
+    my $message_id = sprintf "%.10f\@example.net", $timestamp;
+    my $sender = unpack("H*", urandom(8))."\@example.net";
+    print $out
+          "From: <$sender>\r\n"
+        . "To: <recipient\@example.net> \r\n"
+        . "Subject: Hello world! \r\n"
+        . "Date: ". strftime("%a, %e %b %Y %H:%M:%S %z", localtime($timestamp)). "\r\n"
+        . "Message-ID: ". sprintf("<%.10f\@example.net>", $timestamp)."\r\n"
+        . "\r\n";
+
+    my $len = 1 + int(rand(4095));
+    my $body = unpack("H*", urandom($len));
+    for (my $i = 0; $i < 2*$len; $i += 70) {
+        print $out substr($body, $i, 70), "\r\n";
+    }
+    close($out);
+}
diff --git a/benchmark/run b/benchmark/run
new file mode 100755
index 0000000..4a83c68
--- /dev/null
+++ b/benchmark/run
@@ -0,0 +1,506 @@
+#!/bin/bash
+
+set -ue
+PATH="/usr/sbin:/usr/bin:/sbin:/bin"
+export PATH
+
+unset CHROOT NETNS
+cleanup() {
+    if [ "${CHROOT+x}" ]; then
+        schroot --end-session --chroot="$CHROOT"
+    fi
+    if [ "${NETNS+x}" ]; then
+        ip netns del "$NETNS"
+    fi
+}
+trap cleanup EXIT INT TERM
+
+# create new CHROOT
+DEB_BUILD_ARCH="$(dpkg-architecture -qDEB_BUILD_ARCH)"
+CHROOT="$(schroot -c "unstable-$DEB_BUILD_ARCH-sbuild" -b)"
+ROOTDIR="/run/schroot/mount/$CHROOT"
+
+# create new network namespace and place counters to measure network usage
+ip netns add "${NETNS:="interimap-benchmark"}"
+ip netns exec "$NETNS" nft -f- <<- EOF
+	flush ruleset
+	table inet filter {
+	    counter interimap-in { }
+	    counter interimap-out { }
+	    counter offlineimap-in { }
+	    counter offlineimap-out { }
+	    chain input {
+	        type filter hook input priority 0
+	        iif "lo" ip daddr 127.0.0.1 tcp dport 10143 counter name interimap-in
+	        iif "lo" ip daddr 127.0.0.1 tcp dport 10144 counter name offlineimap-in
+	    }
+	    chain output {
+	        type filter hook output priority 0
+	        oif "lo" ip saddr 127.0.0.1 tcp sport 10143 counter name interimap-out
+	        oif "lo" ip saddr 127.0.0.1 tcp sport 10144 counter name offlineimap-out
+	    }
+	}
+EOF
+ip netns exec "$NETNS" ip addr add "127.0.0.1" dev "lo"
+ip netns exec "$NETNS" ip link set "lo" up
+
+# resize the partition so it can hold the mail stores (you may want to
+# turn swap off too)
+mount -o"remount,size=15G" "/run/schroot/mount/$CHROOT/dev/shm"
+
+# install dependencies
+schroot --directory="/" --chroot="$CHROOT" -r -- \
+    env DEBIAN_FRONTEND="noninteractive" apt-get install \
+        --no-install-recommends --assume-yes \
+            time dovecot-imapd offlineimap \
+            libconfig-tiny-perl libdbd-sqlite3-perl libnet-ssleay-perl \
+            libcrypt-urandom-perl procps
+
+# run a command in the chroot
+jail() {
+    local user="" home=""
+    case "${u:-local}" in
+        local) user="nobody"; home="/dev/shm/nobody";;
+        remote) user="user"; home="/dev/shm/vmail/user";;
+    esac
+    ip netns exec "$NETNS" \
+        schroot --directory="/dev/shm/nobody" --user="nobody" --chroot="$CHROOT" -r \
+            -- env -i PATH="/usr/bin:/bin" USER="$user" HOME="$home" "$@"
+}
+
+# run a command in the chroot in a monitored fashion
+jail_stat() {
+    local e U S M P u="local"
+    local counters="$ROOTDIR/tmp/counters.$1.json"
+    ip netns exec "$NETNS" nft reset counter inet filter "$1-in" >/dev/null
+    ip netns exec "$NETNS" nft reset counter inet filter "$1-out" >/dev/null
+
+    jail time --format="%e\\t%U\\t%S\\t%M\\t%P" --output="/tmp/time.$1" \
+        -- "$@" >/dev/null || true
+    IFS=$'\t' read e U S M P <"$ROOTDIR/tmp/time.$1"
+
+    local i="${NAME:-$1}"
+    local a="${i#* }"
+    [ "$a" = "$i" ] && a="   " || a=" $a"
+
+    printf "%11s%s" "${i%% *}" "$a"
+    printf "  %5.2fs  %6.2fs" "$U" "$S"
+    if [ "${IDLE:-n}" = "n" ]; then
+        printf "  %5.2fs  %4s" "$e" "$P"
+    fi
+    printf "  %8s" "${M}k"
+
+    ip netns exec "$NETNS" nft -j list counters | jq ".nftables
+        | map(select(.counter) | .counter | { key: .name, value: {packets, bytes} })
+        | from_entries" >"$counters"
+
+    local ib ip ob op
+    ib="$(bytes "$(jq ".\"$1-in\".bytes"  <"$counters")")"
+    ob="$(bytes "$(jq ".\"$1-out\".bytes" <"$counters")")"
+    ip="$(_units "$(jq ".\"$1-in\".packets"  <"$counters")" 1000)"
+    op="$(_units "$(jq ".\"$1-out\".packets" <"$counters")" 1000)"
+    printf "  %8s / %-7s" "$ob" "$ib" # inverse for the client's perspective
+    printf "  %8s / %-7s" "$op" "$ip"
+    printf "\\n"
+}
+
+# display metrics headers
+headers() {
+    declare -a h=("  user" " system")
+    if [ "${IDLE:-n}" = "n" ]; then
+        h+=( "  real" " CPU" )
+    fi
+    h+=( " max RSS" " traffic (in/out) " " packets (in/out) " )
+    local x="offlineimap -q" i
+
+    printf "%s" "${x//?/ }"
+    for i in "${h[@]}"; do
+        printf "  %s" "$i"
+    done
+    printf "\\n"
+
+    printf "%s" "${x//?/-}"
+    for i in "${h[@]}"; do
+        printf "  %s" "${i//?/-}"
+    done
+    printf "\\n"
+}
+
+# install Dovecot's "system" configuration and start the server
+install -onobody -gnogroup -m0700 --directory \
+    "$ROOTDIR/dev/shm/dovecot" \
+    "$ROOTDIR/dev/shm/vmail" \
+    "$ROOTDIR/dev/shm/nobody"
+
+install -onobody -gnogroup -m0644 \
+    "./benchmark/dovecot.conf" \
+    "$ROOTDIR/dev/shm/dovecot/config"
+jail /usr/sbin/dovecot -c"/dev/shm/dovecot/config"
+
+install -onobody -gnogroup -m0600 /dev/null \
+    "$ROOTDIR/dev/shm/dovecot/users"
+PASSWORD="$(xxd -l16 -p </dev/urandom)"
+printf "%s:%s:::::\\n" "user" "$PASSWORD" \
+    >"$ROOTDIR/dev/shm/dovecot/users"
+
+# install user configuration for Dovecot, interimap, and offlineimap
+cat >"$ROOTDIR/dev/shm/nobody/.dovecot.conf" <<-EOF
+	log_path = /dev/null
+	mail_home = /dev/shm/nobody
+	mail_location = maildir:~/Maildir
+	ssl = no
+EOF
+
+install -onobody -gnogroup -Dm0700 --directory \
+    "$ROOTDIR/dev/shm/nobody/.config/interimap" \
+    "$ROOTDIR/dev/shm/nobody/.local/share"
+
+cat >"$ROOTDIR/dev/shm/nobody/.config/interimap/config" <<-EOF
+	database = bench.db
+
+	[local]
+	type = tunnel
+	command = doveadm -c/dev/shm/nobody/.dovecot.conf exec imap
+	null-stderr = YES
+
+	[remote]
+	type = imap
+	host = 127.0.0.1
+	port = 10143
+	STARTTLS = no
+	username = user
+	password = $PASSWORD
+EOF
+
+cat >"$ROOTDIR/dev/shm/nobody/.offlineimaprc" <<-EOF
+	[general]
+	accounts = bench
+
+	[Account bench]
+	localrepository = local
+	remoterepository = remote
+
+	[Repository local]
+	type = Maildir
+	localfolders = ~/Maildir2
+
+	[Repository remote]
+	type = IMAP
+	remotehost = 127.0.0.1
+	remotepass = $PASSWORD
+	remoteport = 10144
+	remoteuser = user
+	ssl = no
+	starttls = no
+	# keep the default (no) as it doesn't seem to work with large mailboxes, perhaps
+	# due to https://dovecot.org/pipermail/dovecot/2019-November/117522.html
+	#usecompression = yes
+EOF
+
+# install interimap's development version
+install -oroot -groot -m0755 -Dt "/$ROOTDIR/usr/bin" \
+    ./interimap ./benchmark/random_maildir.pl
+install -oroot -groot -Dm0644 \
+    ./lib/Net/IMAP/InterIMAP.pm "$ROOTDIR/usr/share/perl5/Net/IMAP/InterIMAP.pm"
+
+# create a random mail store at mdbox:~/mail.back
+prepare() {
+    local u="remote" d m n seqs
+    local maildir="/dev/shm/vmail/user/maildir"
+
+    clear
+    jail rm -rf -- "$maildir" "/dev/shm/vmail/user/mail.back"
+
+    for m in "${!MAILBOXES[@]}"; do
+        [ "${m^^[a-z]}" = "INBOX" ] && d="$maildir" || d="$maildir/.$m"
+        jail mkdir -p -- "$d"
+        # create 20% more; will be deleted afterwards (having only
+        # contiguous UIDs might bias the metrics)
+        n="${MAILBOXES["$m"]}"
+        jail random_maildir.pl "$d" $((n+n/5))
+    done
+
+    # convert to mdbox
+    jail doveadm -c"/dev/shm/dovecot/config" -omail_location="maildir:~/maildir" \
+        sync "mdbox:~/mail.back"
+    jail rm -rf -- "$maildir"
+
+    # expunge 20% and purge
+    for m in "${!MAILBOXES[@]}"; do
+        n="${MAILBOXES["$m"]}"
+        seqs="$(shuf -n $((n/5)) -i"1-$n")"
+        jail doveadm -c"/dev/shm/dovecot/config" -omail_location="mdbox:~/mail.back" \
+            expunge mailbox "$m" "${seqs//$'\n'/,}"
+    done
+    jail doveadm -c"/dev/shm/dovecot/config" -omail_location="mdbox:~/mail.back" purge
+}
+
+# populate a clientn from backup mailstore mdbox:~/mail.back (copied to
+# avoid recreating / conversion)
+populate() {
+    local m u="remote" cmd
+    clear
+
+    if [ "${KEEP_BACKUP:-y}" = "n" ]; then
+        jail mv -T "/dev/shm/vmail/user/mail.back" "/dev/shm/vmail/user/mail"
+    else
+        jail cp -aT "/dev/shm/vmail/user/mail.back" "/dev/shm/vmail/user/mail"
+    fi
+
+    # force dovecot to index and compute the state, otherwise the first
+    # thing to query might be disadvantaged
+    jail doveadm -c"/dev/shm/dovecot/config" index "INBOX"
+    jail doveadm -c"/dev/shm/dovecot/config" mailbox status "all" "*" >/dev/null
+
+    u="local"
+    # initial configuration
+    for cmd in "$@"; do
+        case "$cmd" in
+            interimap) jail interimap --quiet 2>/dev/null;;
+            offlineimap) jail offlineimap -u quiet 2>/dev/null;;
+            *) exit 1;;
+        esac
+    done
+}
+
+# remove interimap / offlineimap database and mail store (but keep
+# mdbox:~/mail.back)
+clear() {
+    jail rm -rf -- \
+        "/dev/shm/vmail/user/mail" \
+        "/dev/shm/nobody/.local/share/interimap/bench.db" \
+        "/dev/shm/nobody/.offlineimap" \
+        "/dev/shm/nobody/Maildir" \
+        "/dev/shm/nobody/Maildir2"
+}
+
+# pretty print a number in k/M/G/T etc
+_units() {
+    local n=$(( $1 )) b="$2" s u=""
+    [ $b -eq 1024 ] && s="i" || s=""
+    while [ ${#n} -gt 4 ]; do
+        case "$u" in
+            "") u="k";;
+            k) u="M";;
+            M) u="G";;
+            G) u="T";;
+            *) break;;
+        esac
+        n=$((n/b))
+    done
+    printf "%d%s" "$n" "${u:+$u$s}"
+}
+bytes() { printf "%sB" "$(_units "$1" 1024)"; }
+
+# generate and deliver a random message
+sample_message() {
+    local date="$(date +"%s.%N")"
+    cat <<-EOF
+		From: <sender@example.net>
+		To: <recipient@example.net>
+		Date: $(date -R -d@"$date")
+		Message-ID: <$date@example.net>
+
+	EOF
+    xxd -ps -c30 -l2048 /dev/urandom # 4165 bytes
+}
+deliver() {
+    local m="$1" u="remote"
+    jail doveadm -c"/dev/shm/dovecot/config" exec dovecot-lda -e -m "$m"
+}
+
+# write down markdown title
+title() {
+    local x="$1" h="$2"
+    printf "\\n%s\\n%s\\n" "$h" "${h//?/$x}"
+}
+
+# run benchmark for `interimap` / `offlineimap -q` / `offlineimap`:
+# populate, run optional actions (such as delivery), then sync again in
+# a monitored fashion
+run-all() {
+    local a cmd u q="" NAME=""
+    for cmd in "interimap" "offlineimap -q" "offlineimap"; do
+        populate "${cmd%% *}"
+        case "${cmd%% *}" in
+            interimap) q="--quiet";;
+            offlineimap) q="-u quiet";;
+            *) exit 1;
+        esac
+        for a in "$@"; do "$a"; done
+        NAME="$cmd" jail_stat $cmd $q 2>/dev/null
+    done
+}
+
+
+echo; echo
+title "=" "Single mailbox"
+
+cat <<-EOF
+
+	We create a mailbox on the remote server, populate it with a number of
+	messages, and synchronize it locally.  We then collect metrics for no-op
+	synchronization (i.e., of mailboxes that are already in sync), and
+	reconciliation after receiving a *single* message on the remote server.
+EOF
+
+# generate a message to be used in *all* "Single mailbox" tests
+sample_message >"$ROOTDIR/tmp/msg1"
+activity1() {
+    deliver "inbox" <"$ROOTDIR/tmp/msg1"
+}
+
+
+declare -A MAILBOXES
+for n in 100 1000 10000 100000; do
+    title "-" "$n messages"
+    MAILBOXES=( ["inbox"]="$n" )
+    prepare
+
+    printf "\\n### %s ###\\n\\n" "No-op (in sync)"
+    headers
+    run-all
+
+    printf "\\n### %s ###\\n\\n" "Reconciliation"
+    headers
+    run-all activity1
+done
+
+
+m=75
+echo; echo
+title "=" "$m mailboxes"
+
+cat <<-EOF
+
+	We create $m mailboxes on the remote server, populate them with an equal
+	number of messages, and synchronize them locally.  We then collect
+	metrics for no-op synchronization (i.e., of mailboxes that are already
+	in sync), and reconciliation after the following changes are being
+	applied to the remote server:
+
+	  - 3 *new* messages (two on mailbox #2, one on mailbox #3); and
+	  - 5 existing messages *EXPUNGEd* (two on mailboxes #3 and #4, one on
+	    mailbox #5).
+EOF
+
+# generate more messages to be used in *all* "$m mailboxes" tests
+sample_message >"$ROOTDIR/tmp/msg2"
+sample_message >"$ROOTDIR/tmp/msg3"
+
+activity2() {
+    local u="remote"
+    deliver "mailbox2" <"$ROOTDIR/tmp/msg1"
+    deliver "mailbox2" <"$ROOTDIR/tmp/msg2"
+    deliver "mailbox3" <"$ROOTDIR/tmp/msg3"
+    # intentionally modify the remote only because not all local backend speak IMAP
+    jail doveadm -c"/dev/shm/dovecot/config" expunge mailbox "mailbox3" "1:2"
+    jail doveadm -c"/dev/shm/dovecot/config" expunge mailbox "mailbox4" "1,3"
+    jail doveadm -c"/dev/shm/dovecot/config" expunge mailbox "mailbox5" "*"
+}
+
+for n in 100 1000 10000; do
+    title "-" "$n messages per mailbox"
+
+    MAILBOXES=( ["inbox"]="$n" )
+    for ((i=2; i<=$m; i++)); do
+        MAILBOXES["mailbox$i"]="$n"
+    done
+    prepare
+
+    printf "\\n### %s ###\\n\\n" "No-op (in sync)"
+    headers
+    run-all
+
+    printf "\\n### %s ###\\n\\n" "Reconciliation"
+    headers
+    run-all activity2
+done
+
+
+title "=" "Live synchronization"
+timeout=$((6 * 3600))
+step=5
+
+MAILBOXES=( ["inbox"]=100000 ["xlarge"]=100000 )
+for ((i=0; i<10; i++)); do
+    MAILBOXES["large$i"]=10000
+done
+for ((i=0; i<20; i++)); do
+    MAILBOXES["medium$i"]=5000
+done
+for ((i=0; i<45; i++)); do
+    MAILBOXES["small$i"]=2000
+done
+for ((i=0; i<20; i++)); do
+    MAILBOXES["xsmall$i"]=500
+done
+
+n=0
+for i in "${MAILBOXES[@]}"; do
+    n=$(( n + i ))
+done
+
+cat <<-EOF
+
+	${#MAILBOXES[@]} mailboxes, $n messages in total:
+
+	  - 2 with 100000 messages;
+	  - 10 with 10000 messages;
+	  - 20 with 5000 messages;
+	  - 45 with 2000 messages; and
+	  - 20 with 500 messages.
+
+	The two local mail stores (respectively for [InterIMAP] and
+	[OfflineIMAP]) are initially in sync with the remote server, and we keep
+	long-running “autorefresh” synchronization processes alive for 6h, with
+	updates being regularly applied to the remote server: every $step seconds,
+
+	  - a new message is delivered to a random mailbox with 5% probability
+	    (once every $((20*step))s on average);
+	  - a random message is EXPUNGEd with 5% probability (once every $((20*step))s on
+	    average); and
+	  - a random message is marked as seen with 10% probability (once every
+	    $((10*step))s on average).
+
+	\`interimap\` is configured to sync every *30s*.  \`offlineimap\` is
+	configured to quick sync very *30s*, with a regular sync every *1h*.
+
+EOF
+
+IDLE="y" headers
+prepare
+KEEP_BACKUP="n" populate "interimap" "offlineimap"
+
+IDLE="y" jail_stat interimap --quiet --watch=30 2>/dev/null &
+IDLE="y" jail_stat offlineimap -u quiet -k "Account_bench:autorefresh=0.5" \
+    -k "Account_bench:quick=120" 2>/dev/null &
+
+u="remote"
+timeout=$(( $(date +%s) + timeout ))
+while [ $(date +%s) -lt $timeout ]; do
+    n="$(shuf -n1 -i1-100)"
+    if [ $n -le 5 ]; then
+        # deliver to a random mailbox on the remote
+        m="$(shuf -n1 -e -- "${!MAILBOXES[@]}")"
+        sample_message | deliver "$m"
+    fi
+    n="$(shuf -n1 -i1-100)"
+    if [ $n -le 5 ]; then
+        # expunge a random message on the remote
+        read guid uid < <(jail doveadm -c"/dev/shm/dovecot/config" search all | shuf -n1)
+        jail doveadm -c"/dev/shm/dovecot/config" expunge mailbox-guid "$guid" uid "$uid"
+    fi
+    n="$(shuf -n1 -i1-100)"
+    if [ $n -le 10 ]; then
+        # mark a random message as seen
+        read guid uid < <(jail doveadm -c"/dev/shm/dovecot/config" search all | shuf -n1)
+        jail doveadm -c"/dev/shm/dovecot/config" flags add "\\Seen" mailbox-guid "$guid" uid "$uid"
+    fi
+    sleep $step
+done
+
+jail pkill -TERM -u"nobody" -s0 interimap
+sleep 0.2 # give a chance to print the stats
+jail pkill -SIGABRT -u"nobody" -s0 offlineimap
+wait
diff --git a/doc/benchmark.md b/doc/benchmark.md
new file mode 100644
index 0000000..72f51a4
--- /dev/null
+++ b/doc/benchmark.md
@@ -0,0 +1,279 @@
+% InterIMAP benchmark metrics and comparison
+% [Guilhem Moulin](mailto:guilhem@fripost.org)
+
+The [IMAP `QRESYNC` extension][RFC 7162] allows efficient mailbox
+synchronization, in terms of I/O as well as CPU usage.  In this document
+we give some benchmark metrics to compare [InterIMAP]'s network usage with
+so-called full synchronization solutions such as [OfflineIMAP].  The
+timings are to be taken with a grain of salt, though: they likely won't
+reflect real-world situations as the emails are stored in RAM for this
+benchmark, and all network access is on the loopback interface.  (Moreover
+neither SSL/TLS nor STARTTLS are being used in the below.  They would add
+another 2-3 round-trips per connection.)
+
+These metrics show how [InterIMAP] scales linearly with the number of
+*mailboxes* — pretty much regardless of how many messages they contain (at
+least as long as the server can cope with large mailboxes) — while
+[OfflineIMAP] scales with the number of *messages* on active mailboxes.
+
+While [InterIMAP] performs significantly better (especially given that it
+can be relied upon to synchronize flag changes, unlike [OfflineIMAP]'s
+“quick” mode), it should be noted that efficiency comes at the expense of
+flexibility.  In particular it's not possible to exclude old messages from
+synchronization (mailboxes can be excluded but finer granularity is not
+possible).  And of course not all IMAP servers support [`QRESYNC`][RFC 7162]
+and other extensions [InterIMAP] requires.  Furthermore [InterIMAP] is
+single threaded and doesn't use pipelining at the moment.  (Concurrency
+opens a can of worms, and given the below metrics it simply doesn't seem
+worth the trouble ☺)
+
+-----------------------------------------------------------------------
+
+The script used to compute these metrics can be found [there][benchmark-script].
+We use [Dovecot] as IMAP server; the “remote” mailbox store is in
+[multi-dbox][dbox] format (initially populated with random messages of average
+size ~4kiB, and randomly pruned to avoid having only contiguous UIDs) while
+[maildir] is used “locally”.  The configuration files were not tuned for
+performance (however [InterIMAP] takes advantage of Dovecot's support of the
+[IMAP `COMPRESS` extension][RFC 4978] as it is its default behavior).
+
+The *user* (resp. *system*) column denotes the number of CPU-seconds
+used by the process in user (resp. kernel) mode.  The *real* column is
+the elapsed real (wall clock) time.  Network measurements are obtained
+by placing packet counters on the interface.
+
+[RFC 4978]: https://tools.ietf.org/html/rfc4978
+[RFC 7162]: https://tools.ietf.org/html/rfc7162
+[InterIMAP]: interimap.1.html
+[OfflineIMAP]: https://www.offlineimap.org/
+[benchmark-script]: https://git.guilhem.org/interimap/plain/benchmark/run
+[Dovecot]: https://dovecot.org
+[dbox]: https://wiki.dovecot.org/MailboxFormat/dbox
+[maildir]: https://wiki.dovecot.org/MailboxFormat/Maildir
+
+-----------------------------------------------------------------------
+
+Single mailbox  {#single-mailbox}
+==============
+
+We create a mailbox on the remote server, populate it with a number of
+messages, and synchronize it locally.  We then collect metrics for no-op
+synchronization (i.e., of mailboxes that are already in sync), and
+reconciliation after receiving a *single* message on the remote server.
+
+[OfflineIMAP]'s network usage remains low in “quick” mode for large
+mailboxes that are already in sync, but as soon as a mail arrives the
+performance degrades by *several orders of magnitude*.  On the other
+hand [InterIMAP] has very little overhead on large mailboxes (also
+memory-wise), and when a message is delivered there is barely more
+traffic than what's required for the transfer of said message.
+
+100 messages
+------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.05s    0.01s   0.07s   85%    21368k     1439B / 1017B          13 / 15
+offlineimap -q   0.04s    0.01s   0.27s   23%    19748k     2497B / 1236B          16 / 20
+offlineimap      0.05s    0.01s   0.32s   22%    19268k     10kiB / 1456B          21 / 23
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.08s   83%    21116k     4516B / 1412B          17 / 19
+offlineimap -q   0.06s    0.00s   0.32s   22%    19968k     15kiB / 1670B          23 / 26
+offlineimap      0.06s    0.00s   0.32s   22%    18616k     14kiB / 1284B          25 / 19
+
+1000 messages
+-------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.05s    0.01s   0.07s   84%    21204k     1449B / 965B           13 / 14
+offlineimap -q   0.06s    0.01s   0.33s   24%    19068k     2664B / 1236B          19 / 20
+offlineimap      0.09s    0.02s   0.37s   30%    19868k     75kiB / 1508B          26 / 24
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.08s   78%    21212k     4524B / 1333B          17 / 16
+offlineimap -q   0.08s    0.03s   0.33s   37%    22284k     80kiB / 1775B          29 / 28
+offlineimap      0.10s    0.01s   0.32s   36%    20116k     80kiB / 1597B          24 / 25
+
+10000 messages
+--------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.09s   75%    20980k     1449B / 965B           13 / 14
+offlineimap -q   0.10s    0.03s   0.37s   37%    36708k     2719B / 1184B          20 / 19
+offlineimap      0.50s    0.09s   0.78s   75%    45424k    746kiB / 2080B          37 / 35
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.12s   54%    21136k     4530B / 1205B          17 / 16
+offlineimap -q   0.51s    0.08s   0.76s   77%    42860k    751kiB / 2608B          43 / 44
+offlineimap      0.62s    0.16s   0.88s   89%    47996k    750kiB / 2222B          38 / 37
+
+100000 messages
+---------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.16s   38%    21080k     1441B / 1017B          13 / 15
+offlineimap -q   1.06s    0.10s   1.40s   83%   201376k     2722B / 1236B          20 / 20
+offlineimap      4.88s    0.83s   5.23s  109%   280716k   7626kiB / 5564B         138 / 102
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.48s   15%    22876k     4532B / 1362B          17 / 19
+offlineimap -q   5.09s    0.75s   5.38s  108%   277336k   7637kiB / 9941B         261 / 185
+offlineimap      4.92s    0.76s   5.22s  108%   279592k   7631kiB / 5603B         144 / 102
+
+-----------------------------------------------------------------------
+
+75 mailboxes  {#multi-mailbox}
+============
+
+We create 75 mailboxes on the remote server, populate them with an equal
+number of messages, and synchronize them locally.  We then collect
+metrics for no-op synchronization (i.e., of mailboxes that are already
+in sync), and reconciliation after the following changes are being
+applied to the remote server:
+
+  - 3 *new* messages (two on mailbox #2, one on mailbox #3); and
+  - 5 existing messages *EXPUNGEd* (two on mailboxes #3 and #4, one on
+    mailbox #5).
+
+The results are not surprising given the metrics from the [above
+section](#single-mailbox).  In “quick” mode [OfflineIMAP] still performs
+reasonably well when the mailboxes are in sync (even though it iterates
+through each mailbox and the extra roundtrips increase network traffic
+compared to the single mailbox case), but performance decrease
+significantly when a message is delivered to a large mailbox.  Once
+again [InterIMAP] has very little network overhead regardless of mailbox
+size; it does take longer on very large mailboxes, but the bottleneck is
+the IMAP server ([InterIMAP] is just rolling thumbs waiting for Dovecot
+to compute `STATUS` responses).
+
+100 messages per mailbox
+------------------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.06s    0.00s   0.12s   55%    21712k     1949B / 898B           11 / 13
+offlineimap -q   0.32s    0.08s   0.43s   92%    22400k     36kiB / 7260B          93 / 99
+offlineimap      0.97s    0.32s   1.32s   98%    22648k    606kiB / 19kiB         243 / 251
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.07s    0.00s   0.15s   53%    21860k     10kiB / 1634B          19 / 19
+offlineimap -q   0.34s    0.11s   0.59s   77%    21248k     81kiB / 8697B         109 / 117
+offlineimap      0.93s    0.35s   1.30s   98%    22804k    620kiB / 20kiB         252 / 253
+
+1000 messages per mailbox
+-------------------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.05s    0.01s   0.31s   22%    22028k     1944B / 898B           11 / 13
+offlineimap -q   0.97s    0.22s   1.22s   97%    23920k     36kiB / 7000B          90 / 94
+offlineimap      4.87s    1.54s   5.01s  127%    25040k   5507kiB / 26kiB         393 / 388
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.08s    0.00s   0.29s   28%    22132k     10kiB / 1931B          20 / 19
+offlineimap -q   1.25s    0.32s   1.45s  108%    27276k    344kiB / 9038B         119 / 123
+offlineimap      4.72s    1.70s   5.05s  127%    26464k   5521kiB / 27kiB         399 / 392
+
+10000 messages per mailbox
+--------------------------
+
+### No-op (in sync) ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.07s    0.00s   1.57s    4%    21896k     1942B / 898B           11 / 13
+offlineimap -q  12.10s    3.98s  11.67s  137%    58624k     37kiB / 10kiB          94 / 168
+offlineimap     55.49s   23.68s  51.50s  153%    70652k     54MiB / 57kiB        1072 / 996
+
+### Reconciliation ###
+
+                  user   system    real   CPU   max RSS   traffic (in/out)    packets (in/out)
+--------------  ------  -------  ------  ----  --------  ------------------  ------------------
+  interimap      0.08s    0.00s   1.73s    5%    23108k     10kiB / 1624B          20 / 23
+offlineimap -q  14.60s    5.22s  14.00s  141%    64988k   3028kiB / 15kiB         203 / 263
+offlineimap     57.24s   25.92s  53.72s  154%    76560k     54MiB / 89kiB        1981 / 1625
+
+-----------------------------------------------------------------------
+
+Live synchronization  {#live-sync}
+====================
+
+97 mailboxes, 500000 messages in total:
+
+  - 2 with 100000 messages;
+  - 10 with 10000 messages;
+  - 20 with 5000 messages;
+  - 45 with 2000 messages; and
+  - 20 with 500 messages.
+
+The two local mail stores (respectively for [InterIMAP] and
+[OfflineIMAP]) are initially in sync with the remote server, and we keep
+long-running “autorefresh” synchronization processes alive for 6h, with
+updates being regularly applied to the remote server: every 5 seconds,
+
+  - a new message is delivered to a random mailbox with 5% probability
+    (once every 100s on average);
+  - a random message is EXPUNGEd with 5% probability (once every 100s on
+    average); and
+  - a random message is marked as seen with 10% probability (once every
+    50s on average).
+
+`interimap` is configured to sync every *30s*.  `offlineimap` is
+configured to quick sync very *30s*, with a regular sync every *1h*.
+
+                 user    system   max RSS   traffic (in/out)    packets (in/out)
+-----------  --------  --------  --------  ------------------  ------------------
+  interimap    12.95s     0.26s    24276k    743kiB / 257kiB       2207 / 4143
+offlineimap  5327.79s  1495.78s   394044k    942MiB / 7840kiB       87k / 126k
+
+Long-lived synchronization for large and busy mail stores is where
+[InterIMAP] truly shines, in terms of CPU as well as network usage.
+(The amount of CPU time spent in kernel mode is so low because the
+process spends most of its time sleeping or in blocking calls waiting
+for the server to compute `STATUS` responses.  Smart servers like
+Dovecot should cache states though, hence are able to serve these
+responses quickly.)  Thanks to the [`QRESYNC`][RFC 7162]-based
+synchronization there is no need for complex client-side computation,
+nor for sending vast amount of data over the network.  (To be fair,
+while the amount of CPU time spent in user mode remains low, the local
+IMAP server might do a bit of extra work which is not counted here.  But
+here again caching helps avoid expensive directory traversal.)   The
+performance gain is most appreciated for battery-powered devices, as
+well as devices behind slow and/or high-latency network connections ☺.
+Moreover [InterIMAP] *does* synchronize flag updates at every step, while
+[OfflineIMAP] normally skips these in “quick” mode so might *delay* flag
+updates for up to one hour.
diff --git a/doc/getting-started.md b/doc/getting-started.md
index 371449d..e20b71d 100644
--- a/doc/getting-started.md
+++ b/doc/getting-started.md
@@ -26,8 +26,8 @@ not*.  Instead, InterIMAP needs an [IMAP4rev1] server on *both* peers
 to synchronize.  This may sound like a severe limitation at first, but by
 seeing both local and remote mail storage though the same “IMAP lens”,
 InterIMAP is able to take advantage of the abstraction layer and
-perform significant optimizations, yielding much faster synchronization.
-(*TODO* link to benchmark.)
+perform significant optimizations, yielding [much faster](benchmark.html)
+synchronization.
 *Note*: InterIMAP uses the [Quick Mailbox Resynchronization][RFC 7162]
 extension for stateful synchronization, hence won't work on IMAP servers
 that don't advertise support for that extension.
@@ -226,8 +226,9 @@ update is requested every minute.  Thanks to the [`QRESYNC`][RFC 7162]
 IMAP extension a status update scales linearly with the number of
 mailboxes (unlike [OfflineIMAP] *not* with the number of messages).  And
 thanks to the `COMPRESS` extension, the typical volume of data exchanged
-is rather small (*TODO* metrics).  You may even want to override the
-default settings and reduce the interval between status updates to 20s:
+[is rather small](benchmark.html#live-sync).  You may even want to
+override the default settings and reduce the interval between status
+updates to 20s:
 
     $ mkdir -p ${XDG_CONFIG_HOME:-~/.config}/systemd/user/interimap.service.d
 <!-- -->
@@ -266,7 +267,7 @@ Other use-cases:
 
 Benchmarks:
 
-:   *TODO*
+:   [Benchmark metrics and comparison](benchmark.html)
 
 Manual
 
diff --git a/doc/interimap.1.md b/doc/interimap.1.md
index ee92668..5cc06a8 100644
--- a/doc/interimap.1.md
+++ b/doc/interimap.1.md
@@ -192,7 +192,7 @@ Options
 
 :   Show the version number and exit.
 
-Configuration file
+Configuration file  {#configuration-file}
 ==================
 
 Unless told otherwise by the `--config=FILE` command-line option,
@@ -429,7 +429,7 @@ Valid options are:
 :   File containing trusted certificates to use during server
     certificate authentication if `SSL_verify=YES`.
 
-Supported extensions
+Supported extensions  {#supported-extensions}
 ====================
 
 `interimap` takes advantage of servers supporting the following
@@ -439,7 +439,7 @@ extensions to the [IMAP4rev1 protocol][RFC 3501] (those marked as
  * `LITERAL+` ([RFC 2088], recommended);
  * `MULTIAPPEND` ([RFC 3502], recommended);
  * `COMPRESS=DEFLATE` ([RFC 4978], recommended);
- * `NOTIFY` ([RFC 5465], recommended);
+ * `NOTIFY` ([RFC 5465]);
  * `SASL-IR` ([RFC 4959]); and
  * `UNSELECT` ([RFC 3691]).
 
diff --git a/doc/pullimap.1.md b/doc/pullimap.1.md
index d40ece8..5028a14 100644
--- a/doc/pullimap.1.md
+++ b/doc/pullimap.1.md
@@ -71,7 +71,7 @@ Options
 
 :   Show the version number and exit.
 
-Configuration file
+Configuration file  {#configuration-file}
 ==================
 
 Unless told otherwise by the `--config=FILE` command-line option,
@@ -249,7 +249,7 @@ Valid options are:
 :   File containing trusted certificates to use during server
     certificate authentication if `SSL_verify=YES`.
 
-Control flow
+Control flow  {#control-flow}
 ============
 
 `pullimap` opens the *statefile* corresponding to a given configuration
diff --git a/doc/template.html b/doc/template.html
index dbcc0e6..41bf3d7 100644
--- a/doc/template.html
+++ b/doc/template.html
@@ -20,6 +20,9 @@ $endif$
     span.underline{text-decoration: underline;}
     div.column{display: inline-block; vertical-align: top; width: 50%;}
     pre{tab-size: 4; -moz-tab-size: 4;}
+    table{width: 100%; margin-bottom: 3ex;}
+    table > thead > tr.header > th{border-bottom: 2px solid #ddd; padding: 8px;}
+    table > tbody > tr        > td{border-bottom: 1px solid #ddd; padding: 6px;}
     @media only screen and (min-width: 600px) {
       .parent {
         float: right;
diff --git a/interimap b/interimap
index 386492e..f9be72d 100755
--- a/interimap
+++ b/interimap
@@ -1154,8 +1154,11 @@ sub callback_new_message($$$$;$$$) {
     my ($idx, $mailbox, $name, $mail, $UIDs, $buff, $bufflen) = @_;
     return unless exists $mail->{RFC822}; # not for us
 
-    my $length = length ${$mail->{RFC822}};
+    my $length = length(${$mail->{RFC822}} // "");
     if ($length == 0) {
+        # the RFC822 attribute can be NIL or empty (it's an nstring), however
+        # NIL can't be used in APPEND commands, and RFC 3502 sec. 6.3.11
+        # explicitly forbids zero-length messages, so we ignore these here
         msg2($name => $mailbox, "WARNING: Ignoring new 0-length message (UID $mail->{UID})");
         return;
     }
diff --git a/lib/Net/IMAP/InterIMAP.pm b/lib/Net/IMAP/InterIMAP.pm
index ef1c20b..1bff06e 100644
--- a/lib/Net/IMAP/InterIMAP.pm
+++ b/lib/Net/IMAP/InterIMAP.pm
@@ -1111,7 +1111,7 @@ sub set_cache($$%) {
         if ($k eq 'UIDVALIDITY') {
             # try to detect UIDVALIDITY changes early (before starting the sync)
             $self->fail("UIDVALIDITY changed! ($cache->{UIDVALIDITY} != $v)  ".
-                        "Need to invalidate the UID cache.")
+                        "Need to invalidate the UID cache for $mailbox.")
                 if defined $cache->{UIDVALIDITY} and $cache->{UIDVALIDITY} != $v;
         }
         $cache->{$k} = $v;
@@ -1819,7 +1819,7 @@ sub _update_cache_for($$%) {
         if ($k eq 'UIDVALIDITY') {
             # try to detect UIDVALIDITY changes early (before starting the sync)
             $self->fail("UIDVALIDITY changed! ($cache->{UIDVALIDITY} != $v)  ".
-                        "Need to invalidate the UID cache.")
+                        "Need to invalidate the UID cache for $mailbox.")
                 if defined $cache->{UIDVALIDITY} and $cache->{UIDVALIDITY} != $v;
             $self->{_PCACHE}->{$mailbox}->{UIDVALIDITY} //= $v;
         }
diff --git a/pullimap b/pullimap
index 1dc4b9e..ee2168d 100755
--- a/pullimap
+++ b/pullimap
@@ -166,7 +166,7 @@ sub sendmail($$) {
              );
 
     print STDERR "C: [...]\n" if $CONFIG{debug};
-    if ($$rfc822 eq '') {
+    if (!defined $$rfc822 or $$rfc822 eq "") {
         # RFC 5321 section 4.1.1.4: if there was no mail data, the first
         # "\r\n" ends the DATA command itself
         $SMTP->printflush("\r\n.\r\n") or die;
@@ -175,17 +175,18 @@ sub sendmail($$) {
         my $length = length($$rfc822);
         while ((my $end = index($$rfc822, "\r\n", $offset) + 2) != 1) {
             my $line = substr($$rfc822, $offset, $end-$offset);
-            # RFC 5321 section 4.5.2: the character sequence "\r\n.\r\n"
-            # ends the mail text and cannot be sent by the user
-            $SMTP->print($line eq ".\r\n" ? "..\r\n" : $line) or die;
+            # RFC 5321 sec. 4.5.2: if the line starts with a dot, double it
+            $line = ".".$line if substr($line, 0, 1) eq ".";
+            $SMTP->print($line) or die;
             $offset = $end;
         }
         if ($offset < $length) {
             # the last line did not end with "\r\n"; add it in order to
             # have the receiving SMTP server recognize the "end of data"
-            # condition.  See RFC 5321 section 4.1.1.4
+            # condition.  See RFC 5321 sec. 4.1.1.4
             my $line = substr($$rfc822, $offset);
-            $SMTP->print(($line eq "." ? ".." : $line), "\r\n") or die;
+            $line = ".".$line if substr($line, 0, 1) eq ".";
+            $SMTP->print($line, "\r\n") or die;
         }
         $SMTP->printflush(".\r\n") or die;
     }
diff --git a/tests/pullimap/t b/tests/pullimap/t
index 7ae0c5f..79da3e0 100644
--- a/tests/pullimap/t
+++ b/tests/pullimap/t
@@ -6,12 +6,9 @@ step_start "\`pullimap --idle\` refuses to create the state file"
 ! pullimap --idle "remote" || error
 step_done
 
-# make sure remote UIDs are 11-bytes long
-doveadm -u "remote" mailbox update --min-next-uid 1000000000 "$MAILBOX"
-
 # compare mailboxes; can't compare the RFC 3501 TEXT as LMTP adds a
 # Received: header.
-# TODO unset lmtp_add_received_header once avaisable in Sid:
+# TODO unset lmtp_add_received_header once available in sid:
 # https://doc.dovecot.org/settings/dovecot_core_settings/#lmtp-add-received-header
 list_mails_sha256() {
     local u="$1" guid uid
@@ -26,7 +23,59 @@ check() {
         <( list_mails_sha256 "remote" ) \
         || error "mailboxes differ"
 }
+message_from() {
+    local date="$(date +"%s.%N")" sender="$1"
+    cat <<-EOF
+		From: $sender
+		To: <me@example.net>
+		Date: $(date -R -d@"$date")
+		Message-ID: <$date@example.net>
+
+	EOF
+    xxd -ps -l8 /dev/urandom
+}
 
+step_start "Quote envelope sender address"
+declare -a senders=("sender" "first.last" "foo-bar" \"\" "\"x\\\" #&\\\\y\"")
+for s in "${senders[@]}"; do
+    message_from "$s@example.net" | deliver -u "remote" -- -m "$MAILBOX"
+done
+pullimap "remote" || error
+check
+for s in "${senders[@]}"; do
+    grep -F " from <$s@example.net> " <"$STDERR" || error "$s"
+done
+step_done
+
+step_start "Mail without data"
+deliver -u "remote" -- -m "$MAILBOX" </dev/null
+pullimap "remote" || error
+check
+step_done
+
+step_start "Dot-leading lines"
+deliver -u "remote" -- -m "$MAILBOX" <<-EOF
+	From: alice@example.net
+	To: bob@example.net
+	Date: $(date -R)
+    Message-ID: <$(xxd -ps -l8 /dev/urandom)@example.net>
+
+	foo
+	.
+	.bar
+	..baz
+EOF
+# we can't add a test for message data not ending with CRLF, because the
+# LMTP/SMTP client needs to add a CRLF so local and remote message
+# bodies would differ.  that said, while such a message could be added
+# by IMAP and LDA, it's not valid for SMTP (RFC 5321 sec. 4.1.1.4)
+pullimap "remote" || error
+check
+step_done
+
+
+# make sure remote UIDs are 11-bytes long
+doveadm -u "remote" mailbox update --min-next-uid 1000000000 "$MAILBOX"
 
 # Add some messages and sync
 step_start "Fetching messages"
@@ -40,11 +89,11 @@ check
 # same thing, but with some missing messages
 for ((i = 0; i < N; i+=2)); do
     sample_message | deliver -u "remote" -- -m "$MAILBOX"
-    deliver -u "remote" -- -m "$MAILBOX" </dev/null # even seqnum
+    deliver -u "remote" -- -m "$MAILBOX" </dev/null # odd seqnum
 done
 for ((i = 0; i < N; i+=2)); do
     # expunge every other message
-    doveadm -u "remote" expunge mailbox "$MAILBOX" $((N-i+32))
+    doveadm -u "remote" expunge mailbox "$MAILBOX" $((N-i+32+7))
     sample_message | deliver -u "remote" -- -m "$MAILBOX"
 done
 
diff --git a/tests/resume/t b/tests/resume/t
index cb0208c..a281ef3 100644
--- a/tests/resume/t
+++ b/tests/resume/t
@@ -38,7 +38,7 @@ doveadm -u "remote" mailbox status "all" "foo" >"$TMPDIR/foo.remote"
 
 ! interimap || error
 grep -Fx "Resuming interrupted sync for foo" <"$STDERR"
-grep -Fx "local(foo): ERROR: UIDVALIDITY changed! ($uidvalidity2 != $uidvalidity)  Need to invalidate the UID cache." <"$STDERR"
+grep -Fx "local(foo): ERROR: UIDVALIDITY changed! ($uidvalidity2 != $uidvalidity)  Need to invalidate the UID cache for foo." <"$STDERR"
 
 sqlite3 "$XDG_DATA_HOME/interimap/remote.db" >"$TMPDIR/dump2.sql" <<-EOF
 	.dump
diff --git a/tests/run b/tests/run
index 30d20f9..a34e4a9 100755
--- a/tests/run
+++ b/tests/run
@@ -235,11 +235,9 @@ sqlite3() {
 # Sample (random) message
 sample_message() {
     local date="$(date +"%s.%N")"
-    # also try non-conventional addresses for pullimap
-    local sender="$(shuf -n1 -e "sender" "first.last" "foo-bar" \"\" "\"x\\\" #&\\\\y\"" )"
     cat <<-EOF
-		From: <$sender@example.net>
-		To: <recipient@example.net>
+		From: <$(xxd -ps -l6 /dev/urandom)@example.net>
+		To: <me@example.net>
 		Date: $(date -R -d@"$date")
 		Message-ID: <$date@example.net>