how to correct a SMTP banner and mx record difference?

I have inherited a 2003 exhcnage server on 2003 domain controllers.  the smtp banner being sent from the exchange server has its original server name appended but the mx record is using another name.

IE, smtp banner:  mx record:

99% of the time this is not an issue however, i have one domain we cannot send email to and i think this may be the cause.  
We are running a barracuda in front of the email server.  I am looking for the best and cleanest way to correct this issue.  When i tried to change the banner on the email server it seemed to upset the barracuda and was no longer able to receive email.  

can i add another mx record for the same server just with a higher priority?  would this cause a problem or is it not permitted to have two mx records pointing to the same ip address?
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Jamie McKillopConnect With a Mentor IT ManagerCommented:
My experience differs from yours...

I have never encountered a situation where mail was rejected because the sending server doesn't have an MX record. There are plenty of situations where a different server is used to send mail for a domain than to receive mail. None of my sending servers have MX records and I send hundreds of thousands of email per day. None of the major spam filtering / email firewall products I have worked with even have the option to reject a connection based on the sending server not having an MX record. This is because the SMTP RFC states that is is perfectly legal for a sending server to not have an MX records. The RFC states that there must a valid return path, so all you need is a working MX for the domain but it doesn't have to be the same server. It would in fact be against the RFC to reject mail solely on the basis that the sending server doesn't have an MX record.

I'm not saying you haven't encountered this situation, just that it isn't common and that it violates the RFC.


Glen KnightCommented:
I have a guide here that will help you configure your DNS correctly:

If you find the article useful please vote for it :)
Jamie McKillopIT ManagerCommented:

The hostname used in the SMTP banner does not need to match the MX record and would not cause any issues if it doesn't. Are you sending email out through the Barracuda or does it go directly out through Exchange? All you need to make sure is that whatever server you have configured to send out mail has an A record that matches the banner and a PTR record that resolves the public IP to the A record.

Glen KnightCommented:
afraid it can make a difference I have seen some systems do a check in the SMTP banner and if they don't match the mail is rejected.
YankeeFan03Author Commented:
the issue with the mail was indeed on the client side.  
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