User having trouble sending mail via PHP

[imaginit]

I have an account, that does not use our mail servers. They use an external hosted exchange sever somewhere else. Anytime their php scripts try to send email from their domain, i receive an error message like so...

SMTP error from remote mail server after MAIL FROM:<nobody@host>:

553 sorry, your envelope sender domain must exist
or
501 SYNTAX ERROR IN PARAMETERS OR ARGUMENTS

assume that because it is sending the email as nobody@host could be the issue, but I am noto sure. Any advice on how to resolve this issue would be greatly appreciated! Thanks in advance!

Lance

[jayh38]

Do you have the proper mx records setup in their dns zone?
Also test the routing from your box to the remote mx. Ping or telnet
their domain.