interimap: Gracefully ignore messages with NIL RFC822 attribute.

Like we do for zero-length messages.

Closes: #944812.

2 files changed, 5 insertions, 1 deletions

diff --git a/Changelog b/Changelog
index f0c9e50..88181b2 100644
--- a/Changelog
+++ b/Changelog
@@ -105,6 +105,7 @@ 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 NIL RFC822 attribute.
 
  -- Guilhem Moulin <guilhem@fripost.org>  Fri, 10 May 2019 00:58:14 +0200
 
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;
     }