Note: A top-level domain (TLD), sometimes referred to as a top-level domain name (TLDN), is the last part of an Internet domain name; that is, the letters which follow the final dot of any domain name. For example, in the domain name www.example.com, the top-level domain is com (or COM, as domain names are not case-sensitive).
To set up POP access on your iPhone for the first time:
If you already have an account defined, you can add a new mailbox by going to Settings from the home screen, then Mail. There you will find an Add Account link you can use to follow the directions above.
Congratulations! You're done configuring your client to send and retrieve messages.
For any other iPhone related issues, please visit http://www.apple.com/support/iphone/