To change your iPhone or iPad SMTP port settings
- Open the Settings app.
- On the Settings screen, tap the Accounts & Password option.
- Tap the email account you want to change.
- Tap the Account
- Tap SMTP and select the SMTP server you want to modify.
- If you have Use SSL turned on, use port 465. Otherwise turn Use SSL off, and try these other ports for SMTP: 80, 3535, or 25.
- Go to Mail, and check to see if you can send email. If not, repeat steps 1-5 and try a different port.