When I go to send an email it says that the address is denied by the server. What can I do to fix this problem. Thanks.
Welcome to EiP!
You get this problem when you us an ISP provided pop account and you're away from your home network. ISPs block outgoing emails from their server when you're not on the network to prevent spam.
You can try changing the settings on your outgoing server to port 587 instead of port 25, but it didn't help me at all. I finally had to configure a gmail account that would accept emails sent to my ISP provided email address and reply from that address as well.
You can also configure your outgoing server settings to cwmx.com instead of the normal smtp.myprovider.com settings. This will let you send outgoing email directly from your ISP provided email address when you're on the Cingular/ At&t EDGE network, but will prevent you from sending email when you're on WIFI anywhere. It's sort of clunky but it is a workaround.
There's quite a few posts on the Apple/iPhone/discussion forums. You can go to iPhone support at Apple.com to participate in those forums.