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Hostname in Message-ID does not match FQDN for SMTP server.  Does this matter?

Posted on 2007-11-29
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Last Modified: 2013-11-30
We have an SBS machine that we use as our internal mail server.

Recently, we have had a number of emails returned from a number of different recipients.  Reasons for non-delivery are time expired or permission denied.  These are just one-off emails - not part of any bulk mailing activity.

There have also been a number of emails delayed for many weeks - some sent in August have just been delivered to the recipient.

Some of the recipients are using public services like hotmail - so I assume it's not an issue with the recipient servers.

I've double checked all settings on our server...been to DNSstuff.com to check junk email blacklists and made sure reverse DNS is set up correctly.

Retry intervals on the SMTP server are 10 minutes, expiry after 7 days.

All appears to be as it should.

However, one thing I have noticed is that the Message-ID header on our outgoing emails contains a different hostname to the one sent as FQDN, which is the one registered with reverse DNS.

We have two hostnames pointing to our public IP
mail.ourcompany.com
secure.ourcompany.com

Originally, the only host name we used was mail.ourcompany.com and so MX records, SMTP server's FQDN and reverse DNS are setup for mail.ourcompany.com

However, there is a small web application that needs to be accessed by a couple of our customers that runs on our SBS machine - restricted by IP to their offices and also password protected.  We have a SSL certificate for this (public CA) under the hostname secure.ourcompany.com.

So this same certificate has been used in the SBS Connect to Internet wizard for use with Exchange.

As a result, the Message-ID header on outgoing emails has the suffix @secure.ourcompany.com and not @mail.ourcompany.com which can be correctly resolved using rDNS.

Would this cause a problem?


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Question by:devon-lad
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Expert Comment

by:Sembee
ID: 20372925
If the server is announcing itself as secure.domain.com and that resolves to the same IP address then I would suggest that you get everything switched across to that.

Another option would be to stop using the home grown certificate and purchase one for that name. Then setup SBS using your preferred name for mail.

It is probably the FQDN value that is causing the problem.
ESM, Servers, <your server>, Protocols, SMTP. Right click on the default SMTP VS and choose Properties. Then click Delivery and then Advanced. The FQDN should match what the Reverse DNS record says. The wizard never sets it correctly.

Simon.
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by:devon-lad
ID: 20372941
Server is currently announcing itself as mail.ourcompany.com as per reverse DNS

"...FQDN and reverse DNS are setup for mail.ourcompany.com..."

We are not using homegrown

"...SSL certificate for this (public CA)..."

FQDN does match reverse DNS - but it does not match the hostname in the Message-ID headers.
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Sembee earned 250 total points
ID: 20374819
No one scans on the message-id headers. That isn't an issue as far as I am concerned. The message-id reflects the server's real name. You get email from me it will say server4.domain.local and I have no problems with email delivery.

Therefore the message-id is not the cause of your problems.

Simon.
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Author Comment

by:devon-lad
ID: 20380633
Right...that's what I wanted to know.
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