[imp] Update - certain emails blocking ActiveSync on iPhones

[Sebastian Arcus]

Further to my thread from a few weeks ago, this has started happening on 
a second iPhone at the same site. Emails on this iPhone have stopped 
syncing completely 4 days ago.

This time, after the hints from Michael J Rubinsky, I've taken a closer 
look at the inbox of the affected account on a computer, and the email 
immediately after the last message which has synced successfully on the 
phone has the following subject line:

<<PR:63364>><<IR>> Site Inspection Report, Marshalswick, St Albans

There were 7 emails with this subject line - part of a thread. After 
moving them away from the inbox to another folder, the sync resumed 
instantly on the iPhone.

Is it possible that some characters in the subject line above trip 
Horde, or the ActiveSync protocol somewhere? If I reconfigure the iPhone 
to use imap, it syncs all messages of any type, without complaints - so 
the issue seems to be somewhere between ActiveSync, Horde and the Mail 
app on the phone.

Last time when this happened I also tried the Outlook app using 
ActiveSync / Exchange on the iPhone - and that was even worse. It 
refused to download any email. It kept on saying "There is no email 
here" when checking the inbox.

I thought maybe the above sheds a bit more light on this issue. Please 
let me know if any further details are needed. I can collect some debug 
logs, or forward the troublesome email in full if that helps.