In our company we use Mac Outlook 2011 (newest version), PC Outlook 2013 (newest version) and Exchange server 8.3.379.2. The PC Outlook mail content is synchronized properly between my iPhone Exchange mail account and OWA (Outlook Web Access). The content is synchronized basically immediately with no delay.

However, the sync between Mac Outlook 2011 and the rest of the Exchange mail content is not working for me. My colleague has almost identical gear and he doesn't suffer from the problem. We have no idea why.

When I delete a message in Windows-Outlook, then the message gets deleted in my OSX-Outlook in just one second. But if I delete a message in OSX-Outlook, the message may get deleted in Windows-Outlook in 60 seconds, but there are many cases where it doesn't sync some particular differences (in which folder an email message is located) at all. So my Windows-Outlook has ~500 messages in my Inbox and OSX-Outlook Inbox has ~300 messages. I have already tried removing all subfolders in Inbox according to the "best practices" but that didn't have any effect.

What can cause this behaviour?