[sync] Outlook 2013 Seemingly Random Duplicate Emails using ActiveSync

[Tim ODriscoll]

Dear All,

I have several Outlook 2013 users experiencing random duplicate emails  
in their inbox's. There does not appear to be a pattern as far as I  
can tell so far.

My ActiveSync log appears to show the message being pushed down to the  
device twice in different sync sessions:

2015-05-15T08:08:58+01:00 INFO: [7165]  
Horde_Core_ActiveSync_Driver::getMessage(INBOX, 3105)
2015-05-15T08:08:58+01:00 INFO: [7165] Sending MIME Message.
2015-05-15T08:08:58+01:00 INFO: [7165] Checking MIMETRUNCATION: ,  
ServerData: 6700
2015-05-15T08:08:58+01:00 INFO: [7165] Fetching verb for  
<000001d08edd$05ac5100$1104f300$@lambrookschool.co.uk>: Array
<.....>
2015-05-15T08:09:35+01:00 INFO: [26335]  
Horde_Core_ActiveSync_Driver::getMessage(INBOX, 3105)
2015-05-15T08:09:35+01:00 INFO: [26335] Sending MIME Message.
2015-05-15T08:09:35+01:00 INFO: [26335] Checking MIMETRUNCATION: ,  
ServerData: 6700
2015-05-15T08:09:35+01:00 INFO: [26335] Fetching verb for  
<000001d08edd$05ac5100$1104f300$@lambrookschool.co.uk>: Array
<.....>

I've disabled my AV plugin within Outlook 2013 and this morning I've  
disabled all other plugins as the problem persists.

Does anyone have any ideas on how to sort this out?

Many thanks,

Tim