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How can i fix not local host error?

Last Modified: 2013-11-30
Hello Everyone,
I could use some help getting rid of the <EXCHANGE.xxxx.ad #5.5.0 smtp;550 not local host abc123.com, not a gateway> error. This only occurs when attempting to email 1 specific domain. They say the problem is on my side? They have white listed our domain and are having no problems receiving from anyone else that they are aware of. Any suggestions?

1 Watchguard X1250 Firewall
1 Exchange 2003 server
1 Barracuda Anti-Spam Firewall (only set to block incoming)
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Top Expert 2007

Can you check with the site in question if they are doing reverse DNS lookup; also is your external IP address of the firebox different than the SMTP server public IP; if yes, then setting 1-1 NAT for your SMTP Server should resolve the issue.

Please let me know the WSM/WFS version you have and I would list the steps to configure 1-1 NAT.

Thank you.
Expert of the Year 2007
Expert of the Year 2006

That is not an Exchange error message, so the problem is being generated outside of Exchange. Have you tried manually connecting to the remote server using telnet to see if the problem is shown there?


If your question has been answered, pleased remember to accept the answer and close the question.


I will have to get back to you on the reverse DNS lookup. It may take some time to contact their IT dept. According to dnsstuff.com reverse dns resolves our mail ip address with no issues. Not sure if that really tells us anything. External and Public IP are the same.

WSM 8.3.0 - Build 2550
FSM 1.3 - Build 2550
Top Expert 2007

If you are having only one public IP then 1-1 NAT and reverse DNS lookup problem would not be applicable to your case; they would only be applicable if you have a different external IP address of FB than the public IP of your exchange [ns/mx/a anything]

Try using filteredSMTP for outbound SMTP traffic and check if that helps anything.

Thank you.

Could possibly be a bad HELO string, like your server says its name is something unexpected like "localhost" instead of the proper "mail.yourdomain.com" or some such fqdn. Some servers balk at that.


Thanks everyone for your input. It appears there is an issue with our primary DNS server. I am not sure why that company is the only one affected but upon pointing the Exchange server to our secondary DNS the mail went through with no problems. Now I will have to diagnose the DNS problem next.

I will start on that as soon as the brain swelling from this problem subsides...
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