Joe Greco wrote:
On Fri, 18 Dec 2009, Jason Bertoch wrote:
Do metrics exist on how many current installs still rely on the implicit MX?
It's very common for email from web servers to be poorly configured such that it uses the webserver's hostname as the return path's mail domain.
It is very difficult to measure how many current installs rely on the implicit MX, as someone else noted.
On a somewhat different angle of attack:
Even five years ago, it was considered mildly problematic to deploy a hostname where the A pointed someplace incapable of receiving mail, since some "products" (you know who you are) were so poorly written and still in use that they would connect to the A (or "implicit MX" if you prefer) even in the presence of MX records.
Now that another five years have passed, it would be interesting to see how many antiques are still sending e-mail AND are worth talking to. I'm guessing not many.
That suggests that it might well be fine to point A at something that is not capable of receiving SMTP, as long as you have MX records. An arrangement that should always have been practical, of course.
Is anyone actually doing this?
... JG
I'd think this more than common - the A record for the domain quite often is set to point to the same IP as the www. A record where that server isn't running an smtp service. We've certainly got clients who do this, and haven't ever reported it causing problems = one example :- banquo>host -t A www.thehut.com www.thehut.com has address 89.234.46.152 banquo>host -t A thehut.com thehut.com has address 89.234.46.152 banquo>host -t MX thehut.com thehut.com mail is handled by 3 mail.thehutgroup.com. banquo>host -t A mail.thehutgroup.com. mail.thehutgroup.com has address 217.158.230.4 Regards Pete