Bug#878842: cyrus-imapd + Apple Mail causes process bomb

[Jens Georg]

Package: cyrus-imapd
Version: 2.5.10-3

When using Apple Mail (version 10.x or 11.x) against a Cyrus imap
server, it seems that Apple mail does not properly implment the IDLE
command. After a day or so, we have seen that many idling imapd
processes are created, exceeding the maximum number of child
processes that cyrmaster will spawn, preventing any new client to
connect to the mail server.

It seems that upstream cyrus has made a patch for this behavior at
https://github.com/cyrusimap/cyrus-imapd/commit/865199dce1291c612c5b5f3f5957b7800ba863b9
for the 2.5 branch.

We have this patch running locally and it seems to fix the problems
mentioned above.

I am running Debian Scratch version 9.2, updated from Jessie