No matter what past experiences might have been, since mid-2004, you must have the following for out-going SMTP to work:
1. Preferably, you should have a T-Mobile Internet 2 data plan. The Internet 3 VPN plan is not dependable with Treos because of the limited pool of IPs. The free T-Zones is almost certainly not enough, although the T-Zones Pro plan is usually reliable, at least up to the time of this writing, mid 2004. But T-Mobile changes what data plans are blocked or enabled to do. So Internet 2 is best.
2. A login profile at www.t-mobile.com for your mobile number. You must do this, or you cannot get to the next mandatory step.
3. Once logged in, you must click on the MyEmail link and fully configure / integrate your ISP e-mail account into the MyEmail proxy service. (It works much like BlackBerry Web Client and is just as secure. Use it, don't worry. The SMTP server will never work unless you have done this step.)
4. In the Treo's built-in Mail client, you input the following:
-- user name is... mobile number:email address (ex. 5551234567:somename@isp.net)
-- password is... your regular password for your ISP e-mail server. That would be defined within your desktop computer's e-mail client. Or ask your ISP to remind you of your password.
-- incoming and outgoing server names are identical... myemail.t-mobile.com. It's best not to mix and match your ISP's incoming serve with T-Mobile's SMTP server name, but it's not a disaster in most cases.
-- In the Treo's Mail "Advanced" tab, you must check mark SSL for outgoing server, but you don't have to enter a user name again (near the bottom of the screen) since T-Mobile's MyEmail service doesn't use POP-before-SMTP authentication. However, a few people have developed superstitions that you must have the user name defined in this tab. Does no harm to put it in, but honestly it doesn't help either.