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

Note: The images shown here are from an iPhone, but the same process applies to an iPad

1. Start by opening the Settings app
2. Tap the Mail item, then tap the Accounts item
   
3. Tap your mailbox from the list provided
4. Tap on Account
   
   
   
   
5. Under the Outgoing Mail Server heading, tap on the SMTP item
   
   
   
6. Tap the server listed under Primary Server
   
   
   
   
7. Check and update the following:
   1. Use SSL: On
   2. Port: 587
      
      
      
      
8. Tap Done in the top-right to confirm the changes

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