Why do I so often have to restart my MacPro laptop to get mail out of my outbox?

My ISP recently crashed. Since then I have recovered my phone service and internet service.

But my Mail application keeps rejecting my passwords. I've read everything I can find on this subject,

and even managed to move over to iCloud and recover my emails. But this is only a temporary solution,

I suspect, since I have not plans of upgrading to Lion (because I NEED Rosetta!)

Additionally, I do not like iCloud for my email--too many steps compared to the convenience of using Mail

on my two main computers.

I'm very illiterate regarding the computer terms for understanding all this. I was wondering, however, if I should

brave using Time Machine to revert to a prior Mail application. If it fails, will I lose my post-Time machine emails?

And is there a conflict between Mail and iCloud'

I'm already shopping around for a new email provider, since it appears, via the rumor mill, that people without

Lion will be cut off eventually. But I'd like to try to stay with mail.

I cannot see anyway to list my productS--only one choice is there. So here they are: MacPro, MacBook Pro (both with Snow

Leopard 10.6.8) and an iPad2, with probably the latest IOS.