Q Since updating Yosemite, Mail receives messages fine, but can no longer send any out. The Connection Doctor reckons its settings work fine, so what is wrong?
A Sometimes such settings get muddled like this after updates, and some updates to Yosemite seem to have generated various problems connecting to SMTP (outgoing) servers.
If you have an iPad or iPhone which is still working fine, you can compare its settings for sending outgoing mail, and check against those given in your ISP’s support pages.
However even after doing this, some users continue to fail to connect properly. A more drastic approach is to clear the list of SMTP servers and enter the information afresh. You can do that in Mail’s preferences under Accounts: locate the popup menu of SMTP servers in Account Information, and there edit the SMTP Server List from that menu. You are likely to see several old server settings listed, which you should definitely clear.
The drastic solution is to delete all existing SMTP servers and set them up from scratch, using the information provided by the mail service providers. Ensure that you have copies of user names, passwords and other essential information before deleting any.
Updated from the original, which was first published in MacUser volume 31 issue 2, 2015, its final issue.