Fortunately, you can also specify a preferred outgoing mail server for each account in Mac OS X Mail. This SMTP server will then be tried first when you send a message from the account.
Specify a Preferred SMTP Server for a Mac OS X Mail Account
To set a default outgoing SMTP mail server for an account in Mac OS X Mail:
- Select Mail | Preferences... from the menu in Mac OS X Mail.
- Go to the Accounts tab.
- Highlight the account a default outgoing mail server of which you want to specify.
- Make sure the Account information tab is selected.
- Under Outgoing Mail Server (SMTP):, select the preferred server from the drop-down list.
- Click OK.
- Close the Accounts window.

