[horde] Outlook EAS ActiveSync errors

[Nels Lindquist]

I have a number of Outlook EAS clients connecting to Horde ActiveSync
(Horde Groupware Webmail Edition 5.2.22 installed).

I recently noticed the following on the Horde ActiveSync wiki page:

"It is recommended that this server support the QRESYNC server extension
for performance reasons, though it will work without this. It can also
help performance if an IMAP proxy is used. Some IMAP servers like older
Cyrus versions (< 2.4) might support QRESYNC but do not enable per
mailbox MODSEQ by default. Enabling this on these servers will greatly
improve performance."

As the underlying Cyrus IMAPD server is version 2.3.x, QRESYNC was
indeed not enabled by default.

I've manually enabled the CONDSTORE feature for several mailboxes to see
if it would resolve some issues they're having, but they're now
experiencing the following symptoms:

Messages in INBOX and subfolders all synchronize properly, but as soon
as the user replies to a message or sends a new messages, it seems to
lose synchronization and resync all mail messages.

In the ActiveSync per-device log I'm seeing errors like:

"MODSEQ errors including "ERR: IMAP Server error: Current HIGHESTMODSEQ
is lower than previously reported."

and

"ERR: Force restting of state for F5cb7673e: Transition to MODSEQ
enabled server"

Resetting the ActiveSync association through the Horde administrative
interface doesn't help; neither does rebuilding the Outlook profile.

I do have an IMAP protocol log covering the same time period as the
ActiveSync device log, though there are no obvious IMAP errors that I
can see.

----
Nels Lindquist | <nlindq at maei.ca>