Y-Mail Problems

[garys11#IM]

I did a search for a answer but either I missed it or no one has this problem.
Everytime I try to send a email though one on my yahoo email accounts, I get it kicked back to me (server failure). I am able to receive mail but can not send.
I am running a unlocked (TMO)/ 2G/OS 3.0
Thank you to all that can help me...