Improve your email overall, fix issues with receiving or sending email. Or generally make things work if you simply don’t know how OS X Mail works or is supposed to work. This post will outline a number of things to look at which may improve your overall mail usage but also will be helpful if things go bad. This post is particularly useful if you use IMAP/POP email combined with SMTP (for sending). Exchange accounts are a whole different kind of animal and are not covered in this article.
If your email is not working at all
Interpreting the error
Connection doctor lists all your email accounts 2 times, one for incoming (IMAP/POP) and one for outgoing (SMTP) email. In the above example I deliberately broke one account – It’s marked with a red dot and the error with the likely cause is displayed behind it.
Things to check
Review the screenshots below – And especially the items marked with a red arrow which are important for a working mail account. Reach these menus via the Mail > Preferences menu.
Common Email ports:
Secure IMAP – port 993
Secure POP3 – port 995
Secure SMTP – port 465
Standard IMAP – port 143
Standard POP3 – port 110
Standard SMTP – port 25 / 587
IMAP vs. POP3
If you receive your email on multiple devices you should try to avoid POP3. IMAP will sync your email via the mail server to all your devices. POP3 can not do that and will download emails on the device that asks for them first. Leaving the other devices without those emails. Having an asynchronous email setup like that is very inefficient and works very annoying. You never know where your mail is. Most providers support IMAP these days. So if you can, ditch POP3.
Security and privacy concern
Equally important, always use the secure option. This is especially true if you regularly communicate with customers and such. It just adds that extra bit of security. Check with your email provider if this is possible – Most support this too these days. Sometimes for a small fee.
Using it your email is encrypted end-to-end so nobody can snoop around and you can feel more comfortable sending eyes-only information.
Saving the settings
Saving the settings is done by either moving to another tab (top), selecting another account (left sidebar) or closing the settings window completely and confirming at the prompt.
Note: This post applies to pretty much every recent version of Mac OS X. So Tiger, Leopard, Snow Leopard, Lion, Mountain Lion, Mavericks, Yosemite and El Capitan *all* have the connection doctor tool. Probably older versions too.