Error logged by mail source agent:
"CFolder::Synchronize Error -2147219956
The OST has reached its maximum size. To reduce the amount of data in this OST, start Outlook in offline mode, select some items that you no longer need, permanently (shift + del) delete them, then re-sync this folder. (Microsoft Exchange Server Information Store) File: 'aeMAPIFolder.cpp' Line: '508' (Folder: 'Deleted Items', SourceKey: 'C73291EA4E6ED111950900A0C969B0D70000000014C6')"
This is due to the default quota of 2GB exceeded for the OST file.
Refer to the following Microsoft KB articles:
Article ID 832925 - "How to configure the size limit for both (.pst) and (.ost) files in Outlook 2003":
Article ID 288283 - "Both offline files and personal folders files stop accepting data in Outlook 2002":