This article will step you through how to update the SMTP port used by the Mail app in Mac OS.
Don't use Mac OS? Check the help topics for your device or Operating System.

1. Start by opening the Mail app
2. Open the Mail menu and select the Preferences menu item
   
   
3. Click the Accounts icon, and select your mailbox from the list provided
   
   
   
   
4. Under the Outgoing Mail Server (SMTP) heading, check and update the following:
   1. Port: 587
   2. Use TLS/SSL: Checked
      
      
      
      
5. Click the Save button to confirm the changes

Still stuck? Log a support call using the 'Create new ticket' option above!