I use this technique but use an alternate port for the SMTP server. ISPs often block the ability to use a different SMTP server while on their network by blocking the traditional SMTP port of 25. Even if your ISP doesn't block port 25 it doesn't mean you might always be connected to an ISP--via WiFi--that doesn't block it.I finally got this to work. My ISP is roadrunner. Could not send from my roadrunner account via EDGE. Didn't want to switch back and forth. SO...
Opened a Gmail account. Went into settings and set the Gmail account to send as my roadrunner account as default. Had to wait for confirmation email from Gmail. Went into my iPhone mail settings for the roadrunner account. Left incoming mail server alone. Changed outgoing mail server to "smtp.gmail.com" with username as "myusername@gmail.com" (you have to include the @gmail.com) and entered my password. In advanced, set outgoing uses SSL to ON with authentication as "Password". Now I can send from both EDGE and WiFi and the sent mail has my roadrunner address. Haven't tried to send yet from a WiFi other than my home.
So instead using Gmail via port 25 I use its optional port choice of 587. In fact SMTP is about all I use Gmail for lately.
What I did on my iPhone is change outgoing mail server on all accounts to:
smtp.gmail.com:587
(Plus the SSL part mentioned above.)
I also set my normal email address so that the reply-to address is what I want, and not my Gmail address via Gmail's Web interface. This works but Outlook displays "Your Name[yourname@gmail.com] on behalf of; Your Name [yourname@yourISP.com]" on received mail which might suck if you have a strange Gmail address.
Seems to work fine, the only issue is the "on behalf of" thing.
--
Mike