Can't send email - Exchange Active Sync

Can't send email - Exchange Active Sync

I am setting up a new iPhone and trying to use the Exchange Active Sync Functionality so that I can get push email.

Receiving email works fine but when I try to send I get the following error:

"Cannot Send Mail - The message was rejected by the server"

Is there a setting that need to be changed or something to make this work?

Note:  I tried to post this question earlier but I never saw it in the forum so am reposting