Apple Mail flooding the EWS log and the security log

Hello,

I am noticing that one particular user in my environment is flooding the EWS log and the security log on my CAS server (Exchange 2010, latest SP/Rollup). Over the last 24 hours that user generated about 100,000 entries in the EWS log and a similar amount of logon events (ID 4624) and logoff events in the security log. It appears that every EWS log entry (most of which pertain to "SyncFolderItems") is accompanied by a logon/logoff event.

I am watching this kind of behavior for quite some time, so it is not generally caused by an initial folder sync.

The user has Apple Mail on MacOS X/10.8.2.

Can anyone point me to what is causing this problem?

Thanks, Georg.