Clear cache function in Microsoft Outlook for Mac 2011 has deleted emails from the Inbox locally and from the server

Microsoft　Outlook　for　Mac 2011 running on MAC OSx Snow Leopard Version 10.6.8

Version 14.2.2 (120421) – latest available updates applied

Email account configured in Exchange Mode – Microsoft Exchange Server 2007 Service Pack 2

The Inbox was synchronizing with the Exchange server (new messages were arriving and messages could be sent) except that no attachment could be downloaded or opened. The status bar message was displaying „ Downloading attachements 0 of 14 "

We tried to restart, update, reboot even to repair the database, afterwards still the same message appeared.

Next, we cleared the cache for the inbox folder. The messages disapeared from the inbox and start synchronising again. After a while, when the sync was finished we only found 200 emails out of approx. 4000.　 After checking the webmail, we were surprised to find that the emails were missing there also.

Could this clear cache operation determine the email loss?

What about the initial error - Downloading attachements 0 of 14?

Operations were made in the same network with the server therefore no connection problems arised. Network interface WLAN.