Change Outgoing server settings in Mail on Mac
To change these preferences in the Mail app on your Mac, choose Mail > Preferences, click Accounts, click Server Settings, click the outgoing Account pop-up menu, then choose Edit SMTP Server List.
The servers available to you and the accounts that are using them.
Add , Remove
Add or remove a server. Don’t remove a server that’s in use by an account unless you’re ready to select or add another one immediately.
Enter a description of the server. The description appears in the Mail sidebar and any pop-up menu where you choose a server.
Enter the user name you use on the mail server.
Enter the password you use on the mail server.
Enter the name of the mail server.
Automatically manage connection settings
Let Mail automatically manage settings for your email account, such as port numbers and authentication methods, in Mail.
If you deselect this option, you can specify the following, as directed by your email account provider:
Choose a TLS certificate or None. Some SMTP servers require computers that connect to them to provide a certificate proving their identity.
Allow insecure authentication
For accounts that don’t support secure authentication, let Mail use a non-encrypted version of your user name and password to connect to the mail server.
If you change settings, click OK to save your changes.