Email stays in Outbox for long time after it works well for a while.... - Outlook 2007/2010 - SBS 2011 - Exchange 2010 server

Dear All,

Did you experience similar ? Anyone found solution ?

I already reinstall machine, delete and recreate user and mailbox on server, but still same. I use cached mode because users mailbox ~ 1,5-2 GB so I can't turn it off.

Any advice ?

thanks