Some users of OS X Mail, Yosemite, are facing issues where Mail ceases connecting to SMTP servers (that’s for outgoing email). It just happened to my computer today, and the fix indicates it’s a problem with the way Mail is storing/accessing the Keychain. At a guess. Some people also report that Mail repetedly requests the password. The solution below may fix that too.
My rant about Apple Mail issues (excuse me)
In my experience Mail has becoming increasingly unstable and issue prone in the last few iterations of OS X. 10.9.x introduced numerous problems with unread mail count data, and also the count for messages being sent and received. It was widely reported, but Apple failed to solve it. I hoped upgrading to Yosemite would put these issues behind me. Instead, they remained, and other issues have been introduced, also relatively widely reported. Anyway… that’s enough of a rant from me. Let’e get the show on the road…
Fixing SMTP connection issues on Mail
The solution may be relatively simple.
The first thing to try is rebooting your Mac. Some people report that solves the SMTP failure issue. In my case it didn’t help.
Next thing to try is to uncheck “Automatically detect and maintain account settings” for both the incoming and outgoing server settings.
You need to edit each account with the issue, and then edit the SMTP server. Try re-entering the username and password for the SMTP server. If that doesn’t fix it, then note the settings (server name, port number, ssl, etc.) and delete the SMTP account (hit the – button). Then hit the + button and create the account fresh.
In my case, on 6 smtp servers, that fixed the problem. You may need to restart Mail after making those changes. In my case that was not necessary, but some people report it was for that.