What version of SmarterMail are you connecting to. This can be located after logging into the webmail interface and selecting HELP ===> ABOUT SMARTERMAIL.
Please include the complete version, IE: "SmarterMail Enterprise Edition, Version 12.4.5364"
From Microsoft (direct quote, the captions don't make sense):
Sync key mismatch error. To restart sync, disable and re-enable Server ActiveSync on the device for the particular data type that failed (for example, Calendar, Contacts, or Inbox).
This error can be reported if the device was restored from an older backup or the user's Exchange account was restored or moved to a different server.
REQUIRED USER ACTION:
Disable and then re-enable ActiveSync for the data types that are being synchronized by clicking on Start, ActiveSync, Tools, Options, Server
Is any of this applicable to your situation?
Did you previously encounter a data error, either on the server, or at the Outlook installation?
Do you have connectivity issues between the workstation and SmarterMail server, IE: Is the connection sometimes slow, or does it time out and freeze up?
Was the workstation improperly shut down - without Outlook having been properly closed, first? This is a very common error with Mac Outlook 11 installs and requires a database backup and repair prior to any other action.
As Steve suggested, what is your operating system and workstation configuration?
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting