can recieve email but cannot send get this error message?

i can recieve mail but i cant send anything or even forward mail i keep getting this message---------

  this is the error message i recieve…
cannot send message (from field address [[email protected]](mailto:[email protected]) not accepted due to the following reason :      “5.1.0<[email protected]> sender rejected AUP#CMDNS”)

can u please tell me what to do?
i have the correct server names in incoming and outgoing fields i double checked then with my isp and port numbers also r correct…what else do i need to do thnx troy

Yes, [email protected] is not an email address. It is often used to when users post to mailing lists and don’t want to use their real address. It is also used by spammers. Sometimes it is inserted automatically when your contacts are synced with a server and the email address is blank. Lots of reason, but still not a valid address.

Make sure you have a valid email address before sending your message.

Go to Menu > Tools > Accounts and make sure you have your correct email address in the User Information.

yes email is correct and login name and password are correct what do i try next? thnx

i retyped in everything and it seems to be sendng and recieving now where it wasnt last nite so i must have mistyped something?? thnx for ur input seems to have gotten me on the right track i`ll let u kno for sure in a few daz thnx