Resolving email domain with A record ???

[Krelian]

We have some users complaining that some emails they are sending to their clients are bouncing back to them. I did a Nslookup for “MX” records for these domains and found out they don’t exist. Only an “A” record is available. I assume that must be the problem, but the users claims that other clients have no problem sending email to these folks. As a test, I sent a test email myself using my Yahoo account, and that email did go through. So, I can only conclude that somehow, on some email systems out there, they can resolve email domains using only a “A” record even when there is no “MX” record exist. Has anyone seen this before? If so, how can we configure our system so that the email servers can query the “A” record for email domain as well?

 

[Serbtastic]

To send email, the receiving domain MUST have an MX record. Give an example of a domain you are trying to send to that was able to receive email without an MX record. Are you sure you queried the correct DNS server for the MX record?

 

[wbg34]

Test the applicable domain names with

http://www.dnsreport.com/.

If that test indicate any problems, then contact the domain admin and let them know what you've found.

 

[ChrisAC]

Any domain must have an MX record in order for email to work. That MX record will point to a host name which will in turn have an A record which maps the IP address.

For example, tek-tips.com ..

tek-tips.com. 3600 MX 0 mail.tecumsehgroup.com.

mail.tecumsehgroup.com. 3600 A 216.45.19.20

Check it again.

Chris.


**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[Krelian]

Here is example of a domain.

rrdmail.stanford.edu

It has a "A" record but no "MX" record. But my Yahoo account can send emails to username@rrdmail.stanford.edu

Any ideas?

 

[Serbtastic]

rrdmail.stanford.edu may not have email, but stanford.edu does. Internal mail routing is handled by their name servers.

 

[Krelian]

I thought the same, but rrdmail.stanford.edu is running smtp services. You can telnet rrdmail.stanford.edu 25 and it will return with SMTP "Ready" reply.

I just don't understand why my Yahoo account can send email to this domain when it clearly does not have a valid MX record.

 

[Serbtastic]

All mail going to stanford.edu goes to their mail servers, as specified in their MX records. Then, its routed internally to rrdmail.stanford.edu (which has an smtp daemon running, which is why you can telnet to port 25 on this machine).

 

[peterpark]

I think Krelian is right. I have similiar problems with certain domains. Upon checking with one of the ISPs hosting one domain, he says it's because I don't have an A record for my mailserver for my domain name, so since then I've added one. Hopefully, that will resolve my problems with these uunconventional users who relies on A records instead of MX records.