Read the rest of the article for the how-to...
- Make sure you have configured the SMTP server you want to use in Mail's preferences.
- Quit Mail.
- In ~/Library/Preferences/com.apple.mail.plist, find the section corresponding to your SMTP server. It should look similar to this one:
<dict>
<key>AccountType</key>
<string>SMTPAccount</string>
<key>Hostname</key>
<string>smtp.mydomain.com</string>
<key>ShouldUseAuthentication</key>
<string>NO</string>
</dict> - Add the following key/value-pair to this section (replace 2342 with the port number you want to use):
<key>PortNumber</key>
<string>2342</string>

