Tuesday, July 5, 2005

mail to a CNAME domain

A while ago, I learned that the smtp protocol specifies that you can not have a mx record that points at a CNAME record.  And I also learned that you can not have a MX record on a domain that is a CNAME record.

But it also appears that you can't send message to an email address in a domain that is a CNAME record.  When I set up mailman, I created a CNAME host record for something like list.domain.com.  When I sent email to the list address, it appears that the sending smtp server converts the email address to the domain that the CNAME record point to.  So for example:

list    CNAME  domain.com.

emails to address@list.domain.com got changed to address@domain.com.

When I changed the list.domain.com from a CNAME record to a A record and added a mx record for list.domain.com, the email worked correctly.