Postmaster sending email to junk email addresses?

I have 13 emails in "queues" going to bogus email addresses all in a state of retry.  When I look at the message properties, the sender is postmaster@mydomain.com.  I've done an open relay check, and my domain and ip are clear, so how and why is the postmaster account sending these emails?  Running Exchange 2003 by the way.
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jbobstAsked:
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suriyaehnopCommented:
When someone send an email to non-existing mailbox, then postmaster will generate NDR (Non Delivery Status) to inform the sender that their mail to reach the recipient.

This could be a spam sender send to really non-existing mailbox in your enviroment, then postmaster reply the NDR to spam sender
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DipakCommented:
postmaster@ is the system account and is the address that Exchange uses to send back Non Delivery Reports. It is not an account that you created - it is already there and exists on every Exchange server.

If you are seeing a single message in your queue then that is nothing to worry about. A piece of spam has probably got in and your server is trying to return it to the sender, usually that is caused by an Out of the Office message.

The only time you should be worried about postmaster@ messages is if you have a lot (and I mean many 1000s). However that can stopped by setting the recipient filter and tarpit: http://www.amset.info/exchange/filter-unknown.asp

Referenced from below link.

http://forums.msexchange.org/m_1800481268/tm.htm
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jbobstAuthor Commented:
dipak1383, The instructions in your link to set the recipient filter were already done on my server a long time ago, but thanks for the link.

Is there anyway to just tell the server not to try to send NDR to these bogus email accounts or do I just have to leave them in my queue until they expire (or I manually remove them)?
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Simon Butler (Sembee)ConsultantCommented:
@ dipak1383 thanks for ripping off my post from over five years ago.
The actual link is this one: http://exchange.sembee.info/2003/smtp/filter-unknown.asp
I haven't used amset.info for over three years.

Have you checked that recipient filtering is actually working? Use telnet from an external host to see what kind of message you get back.
You don't want to block NDRs as that will cause you more problems.

Does Exchange 2003 receive email from the internet or is there something in between?

Simon.
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jbobstAuthor Commented:
Could anyone point me to the exact telnet commands?  Exchange receives email directly from the internet (our firewall has rules to forward port 25 directly to the exchange server).
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Simon Butler (Sembee)ConsultantCommented:
These are my instructions for a telnet test.
http://semb.ee/telnettest

Put an invalid recipient at your domain in as the recipient. You should get a rejection.
You get anything else and recipient filtering isn't working.

Simon.
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jbobstAuthor Commented:
Sorry for the delay in closing this question.  We have migrated our Exchange Server, so this question is kind of dead for me.  Sorry to leave it open for so long and not follow up.
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