Not all messages being synced in Mail

Hi all,

My Apple Mail is exhibiting some strange behaviour and I haven't been able to get to the bottom of it, I was hoping someone here might have an idea.

In Mail when I open a mail folder and read the message count at the top of the window it suggests there are 8500 messages in the folder, but when I open the same folder using Outlook on PC or Mac or in the web access client there are 8524 messages in the folder.

When I right-click the mail folder and select Get Account Info, it suggests that there are 8524 messages on the server:

I can't figure out why it won't sync the other 24 messages.

This seems to be the case with most of my folders where some messages are missing, for example I have an archive folder where Mail syncs 136 items but in all other clients and on the Get Account Info window it reports as 139 another example where a larger number won't sync is one with 2090 in Mail but 2344 in all other locations.

I have tried a number of things including reindexing mailboxes, setting up the account from scratch and disabling conversation view to name a few.

I should mention that this is connecting to an Exchange 2012 server using Exchange and Apple Mail 8.2 on OS X 10.10.2.

Any advice or insight would be appreciated.