One of our user has very large cache files under \Users\username\AppData\Local\Microsoft\Communicator\username@domain.com
the cache file name are like this: MailItemusername@sipdomain_someRandomDigits.cache
the size of these files can increase to Giga byte.
However, other files under the cache folder have normal size. such as ABS cache, endpointconfiguration cache,GalContacts etc..
What is the MailItem.cache files?