[Webinar] Streamline your web hosting managementRegister Today

x
?
Solved

A Question about resolving MX Records...

Posted on 2008-01-30
3
Medium Priority
?
241 Views
Last Modified: 2010-04-07
Hello,
I have a program I've written which queries name servers for MX Records of domains, and then does the lookup of the A Record from the response. My question is this... if the mx lookup returns no results what should happen? Should I just query the A record for the given domain and try to send mail to that IP, or do I do nothing and consider it a bad domain? Whats RFC dictate? I cant really find anything about it.

Thanks,
Rick
0
Comment
Question by:richardsimnett
  • 2
3 Comments
 
LVL 4

Expert Comment

by:BrianMilnes
ID: 20778063
Hi,
I don't know what the RFC states, but it is perfectly legitimate to not set an MX record for a domain. It may be bad practice, but the DNS record can have an empty MX record. Not every domain has to have an associated e-mail service/host. Sending mail to the A record in such circumstances would be pointless...

Brian
0
 
LVL 14

Accepted Solution

by:
sentner earned 2000 total points
ID: 20778532
Not completely pointless.  Mail servers (such as sendmail) will attempt to send directly to a host name if it exists when it can't find an MX record.  In other words, it will do an A record lookup against the domain name.    See:  http://en.wikipedia.org/wiki/MX_record#MX_Record_and_spam under the section on MX Record and Spam.

Here's the RFC for reference:  http://tools.ietf.org/html/rfc2821
0
 
LVL 4

Expert Comment

by:BrianMilnes
ID: 20778642
Yes, I see the article suggests that not having an MX record but having an e-mail server on the A record host is a way of avoiding some SPAM. And you cite the RFC, that specifies reverting to the A record in the absence of MX records. Thanks for the correction.
0

Featured Post

SMB Security Just Got a Layer Stronger

WatchGuard acquires Percipient Networks to extend protection to the DNS layer, further increasing the value of Total Security Suite.  Learn more about what this means for you and how you can improve your security with WatchGuard today!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The main intent of this article is to make you aware of ‘Exchange fail to mount’ error, its effects, causes, and solution.
This applies to Dell but may also apply to other manufacturers as well. We ran across a few machines that just dropped recently it trust relationship with the server. After doing the basic removing and joining the domain again, it changed to No logo…
To show how to create a transport rule in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Mail Flow >> Rules tab.:  To cr…
The video tutorial explains the basics of the Exchange server Database Availability groups. The components of this video include: 1. Automatic Failover 2. Failover Clustering 3. Active Manager
Suggested Courses

612 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question