I have deleted all my accounts on apple mail and re installed them (yahoo,gmail, hotmail), after having trouble sending emails due to stmp server errors. It worked for the first 10 mins and now back to "stmp servers offline" again, can not send emails! This never happened before. I use Yosemite, which is up to date. Thank you.

Same issues recently. Intermittently. Haven't looked into a solution yet.

Have you guys installed the 10.10.1 update?

The OS X Yosemite v10.10.1 Update improves the stability, compatibility, and security of your Mac. This update:

• Improves Wi-Fi reliability
• Improves reliability when connecting to a Microsoft Exchange server
• Resolves an issue that may prevent Mail from sending messages through certain email service providers
• Addresses an issue prevents connecting to remote computers using Back to My Mac
• Resolves an issue where sharing services, Notification Center widgets and Actions may not be available
• Addresses an issue that could cause Notification Center settings to not be retained after a restart
• Addresses an issue that might prevent the Mac App Store from displaying certain updates
• Addresses an issue that could prevent some Mac mini computers from waking from sleep
• Resolves an issue that might prevent Time Machine from displaying older backups
• Addresses an issue that might prevent entering text in Japanese

^ Yep.

On the run last few days, unable to check it out, and not sending much mail. On to-do-list for this week.

Yes, installed it. Problem developed before the update and again after.

Did you get it sorted?? I entered the smtp data and it worked for a while, now its playing up again.

I had a problem a couple of days ago as well - sorted itself out after an hour

Yes, all is back to normal for now.

When this happened to me it was a matter of backing up the mail I wanted to save then deleting the accounts I had, followed by rebuilding the mailboxes.