evolution mail won't send

Can't send or receive email. Was working fine yesterday, and early this morning. The "send/receive" button is grayed out. When I compose a email, and hit "send", nothing happens, and the email shows to still be in the outbox. I can't retrieve email due to the button being grayed out. Only way to send/receive email is to go to the yahoo web site.

 I downloaded the new version of Evolution (.3.2), but that didn't help. I am afraid to remove the current version for fear of losing my current emails, and addesses.

Thanks,

Brian