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Sunday, August 20, 2006

Exchange: NDR 571 - MAIL REFUSED - Reverse DNS failed; cannot resolve the domain in the HELO command

Summary:

You receive the following NDR when sending to a third party domain:


Your message has encountered delivery problems
to the following recipient(s):

user@externaldomain.com
Delivery failed
571 - MAIL REFUSED - Reverse DNS failed; cannot resolve the (yourmailserverhostname.domain.com) domain in the HELO command.

You verify that your domain does indeed have a Reverse DNS Record.

Cause:

The third party domain is performing HELO lookups, also known as forward DNS lookup. When initiating a SMTP session with a third party domain, the domain validates your domain name by performing a forward check, Domain to IP rather than IP to Domain in reverse DNS lookups. If you designed your DNS namespace for Active Directory and chose a namespace different than your public domain name ie. company.local, your Exchange server by default will advertise as HELO I'm hostname.company.local. The third party domain will attempt to lookup company.local in DNS and will fail and thus reject your E-Mail.

Resolution:

1. Open Exchagne System Manager. Navigate to Administrative Groups, Site, Servers, Servername, Protocols, SMTP, Default SMTP Virtual Server,

2. Highlight Default SMTP Virtual Server, right click properties.

3. Go to the Delivery Tab, and click Advanced Button.

4. In the "Fully-qualified domain name: field, enter your fully qualified external domain name. Click Check DNS to verify that it resolves.

5. Restart SMTP service.

James Chong
MCSE M+, S+, MCTS, Security+
msexchangetips.blogspot.com


How useful was this article? Want to see a tip not listed? Please leave a comment.

12 Comments:

Anonymous Anonymous said...

Excellent - exactly what I needed. Thanks!

5:51 AM  
Anonymous Gerard (from Amsterdam) said...

Thanks, saved me a lot of searching!

6:30 AM  
Anonymous MSvojsik, Praha, Czech republic said...

Cool work James, thank You.

6:54 AM  
Anonymous Anonymous said...

excellent, good job. tank you

2:52 AM  
Anonymous Anonymous said...

excelente, muchas gracias

juancm


excelent, very thanks
juancm

4:24 PM  
Anonymous Steve said...

Yes!! You da' Man!

1:34 PM  
Anonymous Anonymous said...

good job. thank you.

2:41 AM  
Anonymous Anonymous said...

Is there a resoluton for an exchange server running 2007? Procedure might be different? I have this issue with one domain and I tried to change the name to no avail, and most of the searches seem to be with Exchange 2003

1:23 PM  
Anonymous Anonymous said...

Thank you very much. It really helped.

9:30 AM  
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2:54 AM  
Blogger Josu said...

Thanks for your help,

i have this problem but just with one Domain, mailing to other domains worked fine for 6 years. Should I make this test if i only have fails with an unique domain?

Thanks

1:43 AM  

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