550 5.7.1 Delivery not authorized, message refused

[CAskier]

We use a program in our company that automatically sends out emails to
a group of technicians when certain parameters are "out of spec" on
our product. We are running Exchange 2007, single domain environment.
There is a single user who the message does not get delivered to. The
delivery failure message has the code I included in the subject line.
I have compared this user's AD account with another user who is
getting the error messages and have also compared their Exchange
profiles and they are exactly the same. Both users are running the
same OS (WinXP Pro) and the same Outlook client (2007). There are no
security policies that I am aware of that would block this particular
user from receiving the emails. These are internal emails so our spam
filter is not a factor.

Any input would be greatly appreciated.

[d***@gmail.com]

It's a bit late but in case like this, it reflects Exchange tranport rules.

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