Apparently this is a widespread problem. I'm using Mail.app on OS X Mavericks and I can receive but not send form my gmail address. Is there a solution to this?
do you have other mail providers to test for fail/success?
from where are you trying to send mail from? Home or somewhere else?
And has that network you are on ever supported smtp outbound use?
Example: my company provides free wireless at several facilities we have for open customer use. You can surf the web as much as you'd like within reason (we do have av/firewall to block some sites).
However....we do not allow smtp outbound, among other protocols. Mail is not going out via a mail client (outlook, mail, etc). You have to use the web versions for that.
Also found this in quick googling.
https://support.google.com/mail/answer/78775?hl=en
If at some point your mail worked and you made no changes you recall I'd scroll to the bottom and run the telnet testing. If ports aren't connecting with basic telnet there'd be no reason to tear apart your settings when they will fail regardless.