And succeeds if, and only if, the peer certificate SPKI matches one of
the pinned digest values.  Specifying multiple digest values can key
useful in key rollover scenarios and/or when the server supports
certificates of different types (for instance RSA+ECDSA).

The standard error is never sent to /dev/null in debug mode.

Closes: deb#968392

Set "STARTTLS = NO" to ignore.  This is similar to CVE-2020-12398 and
CVE-2020-14093.

For background see https://gitlab.com/muttmua/mutt/-/issues/248 .

Mention the name of the problematic mailbox.  (We may detect the
violation while not in SELECTED state.)

UID EXPUNGE|FETCH|STORE commands are now split into multiple (sequential)
commands when their set representation exceeds 4096 bytes in size.  Without
splitting logic set representations could grow arbitrarily large, and
exceed the server's maximum command size.

This adds roundtrips which could be eliminated by pipelining, but it's
unlikely to make any difference in typical synchronization work.  While set
representations seem to remain small in practice, they might grow
significantly if many non-contiguous UIDs were flagged and/or expunged, and
later synchronized at once.

Furthermore, for MULTIAPPEND-capable servers, the number of messages is
limited to 128 per APPEND command (also subject to a combined literal size of
1MiB like before).

These numbers are currently not configurable.  They're intentionally lower
than Dovecot's default maximum command size (64k) in order to avoid a
deadlock situation after sending 8k-long commands under COMPRESS=DEFLATE:
https://dovecot.org/pipermail/dovecot/2019-November/117522.html .