Nightly thread update mails bouncing... :(
 

In case you're wondering why you didn't get your digest mail...

Seems the admins made a change to the way the nightly thread update e-mails are send out, instead of the previous "[email protected]" as SMTP sender (not the From: !), they used "[email protected]".

Well, that host or domain ("flyertalk4.flyertalk.com"), does not exist in DNS (up to this moment), and as such neatly configured mailservers will have told the offering mailserver to take a hike, since Spammers use(d) similar techniques for ages. As did mine of course...

I'm starting to think I know what mild withdrawal symptoms look like by now... ;)

Up until about a month ago, all of the flyertalk servers sent email as themselves, as in flyertalk4.internetbrands.com. Like you said, there isn't an MX record for that, so any returning mail bounced back to our main IB mail server. This was going on for a loooong time. To fix this, we changed it to flyertalk.com, but since we also have an MX record for mail.flyertalk.com (which the mod's use), there was a conflict. So, sendmail was configured to send as @www.flyertalk.com (notice the www). Well, that makes it so that the server can't sent email to any @flyertalk.com addresses, because it thinks that it should be @www.flyertalk.com. We're currently troubleshooting that, and one possible fix was to change it to servername.flyertalk.com, which didn't correct the problem.

Like I said, we're still working on the problem, but it should be pretty transparent to the end user. Yes, sending email as a domain that doesn't have an MX record can be bad, however it's exactly what the site's been doing for years, so it's not like it is going to make anything worse.

I'm very impressed that you noticed.

Well, problem was/is there's no DNS entry (domain or host!) for those... :(

No need for an MX record, just have an A record for the servername. As long as the RHS (Right Hand Side) can be found in DNS you should be OK.

Hey, I didn't get my digests, and checked my logs.
Occupational hazard for a mail/sys/network engineer. ;)