In OS X Yosemite v10.10 or later, Mail takes the following actions whenever it can't connect to your email provider to send or receive email. This happens in the background, without changing the server settings in Mail preferences. Tries different port numbers for each email protocol (IMAP, POP, SMTP).
Tries using or not using TLS or SSL encryption. Tries using a different authentication methods (Password, MD5, NTLM, Kerberos, None). Tries using your email user name with and without your account's domain name Mail doesn't adjust settings that are working, so it's best to leave this feature turned on. For incoming email:. In Mail, choose Mail Preferences, then click Accounts. Select your email account from the list.
Despite their differences, Apple and Google do work well together when it comes to email. Gmail is free and it has great spam protection. But the Gmail web interface is a bit clunky.
Click the Advanced tab. Use the “Automatically detect and maintain account settings” checkbox to enable or disable this feature. If the checkbox is dimmed, connection settings are always automatically managed for your email provider. For outgoing email.
In Mail, choose Mail Preferences, then click Accounts. Select your email account from the list. Click the Account Information tab. From the Outgoing Mail Server (SMTP) pop-up menu, choose Edit SMTP Server List. Make sure that the account's SMTP server is selected in the list.
Click the Advanced tab. Use the “Automatically detect and maintain account settings” checkbox to enable or disable this feature. If the checkbox is dimmed, connection settings are always automatically managed for your email provider.