Mac Mail.app strips 'From' field when sending mail

Hello, I have a peculiar problem to which I have been unable to find a solution, despite searching far and wide on the Internet.

I access my company's microsoft exchange server email account through mail.app on my mac. In setting up this account, everything was detected easlity and I can send and receive mail without any issue, except one:

When I send an email, my name, in the From field, gets stripped as it gets sent. If I keep the mail as draft, I can see my email address in the From field, but when I finally send the email, that field gets stripped and is now blank.
So now, when I go back and look into my "sent" folder, the from field is blank.

This does not happen when I send email, via the same exchange account, from my iphone or ipad, only mail.app does this. This also does not happen when I send email through my yahoo or gmail account via mail.app.

Any thoughts?