I’m a huge fan of Gmail, which can do everything: Checking your other POP mail, forwarding mail etc. The only one functinality that would be killed is “PUSHING”. I think we gonna see it soon, because Yahoo already did it.
I tried to get Gmail to push to my iPhone, with a couple methods (web2mail Exchange server, YahooPush). After hours of experiment, the best method is forwarding Gmail to mobileMe and let Mobile me do the rest.
I have 3 seperate Email accounts so far (2 for my work and one for Google Apps), so I use Gmail to grab all the email into one single email and then use Gmail filter to labeling it. This lables will shows up in Mail App and iPhone Mail IMAP folder as well.
Then I just forward Gmail into my MobileMe account. This instruction is a good start. The trick is I have to set up SMTP for Gmail on iPhone in order to reply back the message via Gmail account.
For serveral other email accounts forwarding to Gmail like me, I have to set up fake POP mail so that I can use it to reply back via relevant email address.