If you use Gmail, Yahoo Mail, Hotmail or any other free web based email, then you don't need to make any changes on your phone. If you're using Gmail and your mail app keeps prompting you to enter a password, or displays some other error message, you may need to perform an "unlock captcha" of your Gmail account at https://accounts.google.com/DisplayUnlockCaptcha.
If you use a work email or an ISP email (eg @bigpond.com, @johnsplumbing.com.au, @optusnet.com.au) go to the email settings on your phone and change the outgoing mail server / SMTP server to:
Option 1
- smtp.mail.att.net
- Port: 25
- Username: leave this field blank
- Password: leave this field blank
- Use SSL: off/unchecked
- Verify certificate: off/unchecked
Option 2 (if Option 1 doesn't work)
If the above does not work, please try:
- cwmx.com; or
- outbound.att.net
Alternatively, just log in through your ISPs web based email (ie logging in through a web browser).