1. A system for accessing, via an end user device 38 , email messages of an external mail source 48 , the system comprising: at least one direct access proxy 42 , operative to reconcile the email contents of at least one external email source 48 with the email contents of at least one end user device 38 through the use of at least lists of unique email identifiers (UIDs), at least one Partition Database 58 , in data communication with corresponding direct access proxy 42 , and operative to return UID lists reflective of the UIDs of email messages previously received from the external email source 48 and forwarded to a network server 22 of the system (forwarded UID lists), and at least one memory cache, in data communication with a corresponding direct access proxy 42 -Partition Database 58 pair, operative to return forwarded UID lists, and implemented external to each direct access proxy 42 and to each Partition Database 58 ; wherein the direct access proxy 42 : is operative to determine the data reliability of the Partition Database 58 and memory cache, and obtains forwarded UID lists from the memory cache when it determines that the memory cache is at least as reliable as the Partition Database 58 .