Recent (probably MacOS) mail app provoking endless cyrus.index writes on 2.3 server. [WARNING: DKIM validation failed]

[Matt Elson]

> So the exact text after the OK response doesn't matter, but it MUST
> be SP followed by at least 1 TEXT-CHAR.
>
> This is pretty easy to patch in 2.3.x if you're forced to remain
> there for reasons.  It is, of course, fixed in later versions.
>
> Bron.
>
>

I'm seeing this issue in my environment.. I think.  I'm only *fairly* 
sure - I see clients that are identifying themselves as 10.11 causing 
lots of entries showing up in the sync log and a whole lot of index 
churning on.. usually smaller folders, luckily.  I've been trying to 
track down a test machine to validate, but resources are quite limited 
where I am.

But I'm a bit confused about the current working theory as to what's 
causing Mail.app to go into its strange loop.

My Cyrus (RedHat provided 2.3.16-13.el6_6 with a very minor local patch) 
responds to EXPUNGE with "<tag> OK COMPLETED" as near as I can tell.. 
which seems spec compliant if I understand the above.

* OK [CAPABILITY IMAP4 IMAP4rev1 LITERAL+ ID 
MUPDATE=mupdate://redacted.example.com/ AUTH=GSSAPI AUTH=PLAIN 
AUTH=LOGIN SASL-IR COMPRESS=DEFLATE] redacted.example.com Cyrus IMAP 
Murder v2.3.16-Fedora-RPM-2.3.16-13.el6_6 server ready
A0001 login REDACTED PASSWORD
A0001 OK [CAPABILITY IMAP4 IMAP4rev1 LITERAL+ ID 
MUPDATE=mupdate://redacted.example.com/ LOGINDISABLED AUTH=GSSAPI 
AUTH=PLAIN AUTH=LOGIN COMPRESS=DEFLATE ACL RIGHTS=kxte QUOTA 
MAILBOX-REFERRALS NAMESPACE UIDPLUS NO_ATOMIC_RENAME UNSELECT CHILDREN 
MULTIAPPEND BINARY SORT SORT=MODSEQ THREAD=ORDEREDSUBJECT 
THREAD=REFERENCES ANNOTATEMORE CATENATE CONDSTORE SCAN IDLE LISTEXT 
LIST-SUBSCRIBED X-NETSCAPE URLAUTH] User logged in
A0002 SELECT Trash
* FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
* OK [PERMANENTFLAGS (\Answered \Flagged \Draft \Deleted \Seen \*)]
* 4560 EXISTS
* 0 RECENT
* OK [UNSEEN 1]
* OK [UIDVALIDITY 1347582296]
* OK [UIDNEXT 6437]
* OK [NOMODSEQ] Sorry, modsequences have not been enabled on this mailbox
* OK [URLMECH INTERNAL]
A0002 OK [READ-WRITE] Completed
A0003 idle
+ idling
done
A0003 OK Completed
A0004 EXPUNGE
* 4560 EXISTS
* 0 RECENT
A0004 OK Completed


In fact a 2.4.18 install I'm building (I'm using this issue as an excuse 
to prioritize a long time coming upgrade) seems to respond to expunge in 
the same way.


* OK [CAPABILITY IMAP4rev1 LITERAL+ ID ENABLE 
MUPDATE=mupdate://redacted.example.com/ STARTTLS AUTH=LOGIN AUTH=PLAIN 
AUTH=DIGEST-MD5 SASL-IR] redacted.example.com Cyrus IMAP Murder 
v2.4.18-Invoca-RPM-2.4.18-1.el7.centos server ready
A0001 login redacted redacted
A0001 OK [CAPABILITY IMAP4rev1 LITERAL+ ID ENABLE ACL RIGHTS=kxte QUOTA 
MAILBOX-REFERRALS NAMESPACE UIDPLUS NO_ATOMIC_RENAME UNSELECT CHILDREN 
MULTIAPPEND BINARY CATENATE CONDSTORE SORT SORT=MODSEQ SORT=DISPLAY 
THREAD=ORDEREDSUBJECT THREAD=REFERENCES ANNOTATEMORE WITHIN SCAN XLIST 
URLAUTH X-NETSCAPE MUPDATE=mupdate://redacted.example.com/ LOGINDISABLED 
COMPRESS=DEFLATE IDLE] User logged in 
SESSIONID=<redacted.example.com-28519-1445641933-1>
A0002 SELECT Trash
* 0 EXISTS
* 0 RECENT
* FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
* OK [PERMANENTFLAGS (\Answered \Flagged \Draft \Deleted \Seen \*)] Ok
* OK [UIDVALIDITY 1445555503] Ok
* OK [UIDNEXT 1] Ok
* OK [HIGHESTMODSEQ 1] Ok
* OK [URLMECH INTERNAL] Ok
A0002 OK [READ-WRITE] Completed
A0003 idle
+ idling
done
A0003 OK Completed
A0004 EXPUNGE
A0004 OK Completed

(And fastmail's IMAP responds with a OK Completed, and I assume it 
represents the most up to date Cyrus :P)

Am I misunderstanding the theoretical issue?  My IMAP-fu is a little 
rusty these days and I'm a bit bleary eyed so apologies in advance if 
I'm missing something obvious - I'm just testing by typing the commands 
in raw since imaptest is panicking on me and I've not had time to sort 
that out (though my Thunderbird debug log also shows an OK Completed as 
a repsonse).

It does seem from one of the trace logs from the Apple discussion that 
there is a version of Cyrus that responds with just OK, but.. it's not 
all 2.3.x 's at the very least :P.

Sorry again if this noise and thanks in advance for any clarification 
someone can give.

Matt