MS Exchange Server SMTP relay + postfix + mutt problem?

[_Max_]

Hi,

I am trying to set up postfix with mutt so that I can use use a MS Exchange server as a SMTP relay.

The Exchange Server/ SMTP relay requires SASL authentication (AUTH LOGIN), so I compiled postfix with sasl as a use variable, created a /etc/postfix/sasl_passwd file, created a database from that with postmap, put the relevant sasl settings into main.cf and started postfix.

It almost works, except that for some reason, I get this in my /var/log/mail.info:
Aug 31 22:46:13 localhost postfix/smtp[4692]: B72B927562: to=<someone@somewhere.com>, relay=smtp.something.com[blah.blah.blah.blah], delay=0, status=deferred (host smtp.something.com[blah.blah.blah.blah] said: 454 5.7.3 Client does not have permission to Send As this sender. (in reply to MAIL FROM command))

So there is something wrong with my FROM address?

I tried telnetting into the smtp server, and authenticated by hand. That all works fine. But when I try to send stuff, I get exactly this message (454 5.7.3 Client does not have permission to Send As this sender.) if I don't put <> brackets around the FROM email address. If I put my <> brackets around the FROM address, it works, however.

Now that would suggest that somewhere along the line some program should put <> brackets around the FROM address and doesn't. I tried specifying the FROM address in mutt with <> brackets, but to no avail.

Any ideas?