If you don't want to mess with changing SMTP settings every time you switch between EDGE and wifi, and you don't want to pay someone to relay your mail (you already pay your ISP for email priveliges!), just mix your POP and SMTP settings.
If you don't already have one, set up a Gmail account at gmail.com. Gmail kindly lets you use their SMTP server for sending mail any time, from any place.
Then create an "Other" email account on your iPhone. Use the standard POP settings for rr.com (pop-server.yourcity.com, or in this case, pop-server.nyc.rr.com.) Enter your user name and password.
For the SMTP server, use smtp.gmail.com, enter your Gmail user name/password, check "Outgoing uses SSL" in "Advanced", and voila, you're checking mail directly from your Roadrunner account (I find the connection faster and more reliable than forwarding mail to Gmail or having Gmail poll your POP account) and sending mail via Gmail with no IP or location restrictions.
Once you verify this setup works for you, you can delete the original Roadrunner account that the iPhone sync created for you (with its useless-outside-of-your-home-network SMTP settings). You may also need to disable sync for email in itunes, as the account you just create doesn't exist on your computer, and itunes will probably just make a new account with the previous settings you just deleted.
-rkny