The only thing I don't like about the iPhone is the support for MMS messages. It's actually disturbing. So I just have people send MMS messages to a separate email account that I check with the built in iPhone mail.
For example, you can setup a Gmail Account to do something like:
Incoming Mail Server
Use SSL, Authentication Password, Server Port 993
Outgoing Mail Server
Use SSL, Authentication Password, Server Port 587
If you need to send anything, send it to email@example.com or firstname.lastname@example.org