@Douglas Foster: this is an Outlook feature (when you create a new Exchange account in Outlook you can choose to sinc with Exchange Server or not), but SmarterMail support only accounts that have cache option active.
Accounts with cache option disabled give you an error and cant be used in SmarterMail.
SmarterTools claimed that sooner or later it will be supported, but till now there's no news on that.
Gabriele Maoret - Head of SysAdmins at SERSIS
Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)