Though not offered by all free email providers (i.e. Hotmail), Google offers external email reading via the POP3 protocol as part of the Gmail service.
Setting up your iPhone to read your Gmail is fairly simple.
First, insure that POP is enabled in your Gmail account. Go into your Gmail settings and click on the "Forwarding and POP" tab. Once inside, enable POP access (for either new mail or all mail, it's up to you).
Update: Apple iPhone 3G and 3GS now support MMS on AT&T. To activate MMS on your iPhone 3G/3GS with firmware 3.0 follow these instructions. If you wish to update your firmware to 3.1 then MMS should activate during the update process.
One of the most perplexing feature omissions from the iPhone was the lack of support for the MMS protocol. One can only assume that this was a deliberate choice by Apple, though it is hard to determine why.
Contrary to popular belief, the answer is most likely YES!... sort of. Web applications are going to have a huge impact on the iPhone. As users will not be able to install their own software, they will resort to web applications. Instant messaging can be achieved through sites like XS4All's web chat site.
Officially, the iPhone will not provide native instant messaging functionality.
Each iPhone owner can receive a free push IMAP email account from Yahoo!. Push e-mail systems provide an "always-on" capability, in which new e-mail is instantly and transferred to the email client from the server. This will be useful as there is no instant messaging software for the iPhone, such as AIM, ICQ, or IRC.
