Originally Posted by Lightman7

Haven't used t-mobile, but I am a professional geek, so here is my shot:

Almost all ISPs, wireless included, block sending email EXCEPT through their own servers - this is an anti-spam measure. The bottom line is if you don't use their servers to send mail, it won't get delivered. Most companies get around this by using non-standard ports to send mail (port 25 is the default, and the one that is blocked) or by using VPNs. Talk to your company mail administrator to find out what tactics they use to get around mail sending restrictions on external service providers.