I completely agree that having both an MX and an A record for a domain is legal and sensible, when you're talking about a top-level domain (e.g. spamdyke.org). For subdomains and machine names, (IMHO) the need for a complicated configuration has to be pretty big to justify the risk of an administrator breaking the setup because he can't (or doesn't) understand how DNS or MX records really work. I'm sure the GMail team doesn't have this problem but a lot of small hosting companies sure do (think about marketing agencies that host sites they design for their clients).
What I find stupid is what exacttarget.com has done. Email from groupon.com comes from bounce.e.groupon.com. That name has only an MX record, which is bounce-mx.exacttarget.com. Then, bounce-mx.exacttarget.com has both an A and an MX record. The MX record contains the same name, bounce-mx.exacttarget.com. That, IMHO, is stupid. Delete the MX record and just use the A record. It's simpler to understand, test and support. The one benefit of their strange setup is that it uncovered a bug in spamdyke. :) -- Sam Clippinger On 5/12/11 4:32 PM, Dossy Shiobara wrote: > On 5/12/11 5:09 PM, Sam Clippinger wrote: > >> In a nutshell, some >> administrators (groupon.com) have created DNS records that are >> technically legal but logically stupid and they tickle a small bug in >> spamdyke. >> > It's legal and desirable! A FQDN may resolve to an IP address, but the > machine that the IP address points to does NOT handle inbound mail for > that FQDN. You absolutely need an A record *and* an MX record for that > FQDN. > > For example, I have panoptic.com configured with IN A 96.56.31.42, and > IN MX mx1.panoptic.com. mx1.panoptic.com IN A 96.56.31.42, but if I > ever want to redirect inbound mail, I can do so by simply changing the > IN A record for mx1.panoptic.com to point to a different IP. > > This is very common - gmail.com is set up similarly (with both A and MX > records). It's pretty much the standard pattern for DNS configuration. > > Now, I can even define an MX record for mx1.panoptic.com, so if someone > (for some foolish reason) wants to send mail to > [email protected], I can have it routed *elsewhere* and not > actually delivered to the IP of mx1.panoptic.com itself. This is an > unlikely scenario, but one that certainly has very legitimate use cases, > such as third-party email providers. This isn't "logically stupid" at > all - it's exactly this kind of flexibility in the DNS design that makes > outsourced email delivery separate from outsourced email reception possible. > > _______________________________________________ spamdyke-users mailing list [email protected] http://www.spamdyke.org/mailman/listinfo/spamdyke-users
