SMTP Authentication Problems using Apple Mail
Users can't send using Mac Mail using SMTP authentication on port 25
- Launch Apple Mail.
- On the Mail Menu, click Preferences.
- Select Account tabs and select your email account.
- Click the "Server Settings" button under Outgoing Mail Server section.
- Enter the "Outgoing Mail Server" field: mail.domain.com
- Change the port from default 25 to 587.
password: your password
ssl: don't check this box
You may have to quit Mail and restart it for everything to 'take' - do that and when it comes back up, go into preferences and verify that the settings are still set this way for mail.yourdomain.com.
If you're trying to use SSL or a method other than password, you probably won't be able to log in - Mac Mail is one of the mail clients that gets confused if the SSL certificate is self-assigned, so SSL probably won't work. Password authentication with no SSL does work, at least on 10.3 and 10.5.