Email help...can't send emails from my Mogul

[mosttoyswins]

I get my outlook emails pushed to me fine...

However when I try to reply to or send an email I get this error message...

"The server returned the following email message:

550.5.7.1 <whatever address I try to send to>...relaying denied

The following recipients did not receive the message:

janedoe@msn.com (or whoever)

What am I doing wrong and what do I need to do to fix!

Thanks!