I have noticed a peculiar behavior of my google apps domain. Most of the mails come through as you would expect, but over a period of time I have come to the conclusion that mails from certain senders don't come through. After identifying one such sender, whose mails wouldn't come through, I have asked him to try to send me an email and forward the "delivery failure"-response to my regular gmail.
The delivery failure response contained the following snippet:
----- Transcript of session follows -----
<myusername@GHS.L.GOOGLE.COM>... Deferred: Connection timed out with ghs.l.google.com.
This helped me to identify the problem by doing a quick search which led me to this page on Google Apps Help Forum. Indeed, I checked the DNS record for my domain, and
@ was set to ghs.google.com. (CNAME), which it shouldn't be. Changing that to
@ 18.104.22.168 (A)* resolved the problem.
I understand that in the cases where the mail wouldn't come through, my domain name was substituted by it's canonical name through a CNAME lookup, so the mail was sent to
firstname.lastname@example.org instead of
email@example.com. But why did it work for the vast majority of senders? Did the senders whose mail wouldn't come through, use some different kind of mail protocol, some weird DNS settings, or what could it be?
From what I could see by researching the problem on google, this seems to be a wide-spread issue (lots of people complaining about emails from battle.net not coming through, would be one popular example), only that people don't seem to be aware that the problem lies in their own DNS settings, rather then at the senders' side.
So how can this be explained?
* I used this IP because of what I read here, but I think any IP would do the trick. Can anyone confirm this? Note that simply removing the
@ record did not resolve the problem, it had to be changed.