RDNS Problem?

Well, since you redacted information that would actually help someone debug this problem, we can only speculate. I personally am going to speculate that the remote site has broken DNS somewhere, since you claim to have working rDNS.

Thanks for responding.

Yes, I redacted information for privacy reasons. This is a private mailing list.

Checking my Exim log, the message is coming from the other site and I do not have Exim set up for checking RDNS when sending mail. Additionally, I do have Exim set up to check the RDNS when receiving mail, and I can get it from that site just fine - so it looks like the RDNS on their end is working fine.

I also checked both IP's at http://remote.12dt.com/ and both show a valid RDNS entry.

So that doesn't seem to be the problem.

I think what mwalling is suggesting is that the remote mail server's rDNS queries are somehow broken; i.e., although your PTR entry exists, that server cannot see it.

The only other thing I can think is that the hostname your Linode is using for the SMTP transaction is not exactly the same as the one given in the PTR record. For example, your Linode may identify itself as example.com and you have something like this:

example.com.               IN   A     12.34.56.78
78.56.34.12.in-addr.arpa.  IN   PTR   foo.example.com.

There's really nothing wrong with this, but some excessively anal admin may disagree and reject mail from such hosts.

You'll probably need to contact the list owner or postmaster at the remote server to figure out what's going on.

Thanks for the clarification, Vance. Yes, I suppose that can be the problem.

As for the setup - I do have both A, MX and PTR records set up for mail.example.com. Looking closer, the default exim setup is using example.com in the EHLO message. It's never been a problem before - but could it be the problem here?

@jstuckle:

SMTP error from remote mail server after end of data:

host example.com [xxx.xxx.xxx.xxx]: 554 5.7.7 PTR missing .

Note that the remote host isn't complaining about a HELO mismatch, its complaining about what it sees as a lack of PTR records.

Thanks,

Yes, I realize that - but the PTR record exists - I just verified it again through another site. Right now I'm trying to find anything on my end which might be causing the problem.

I would say it's a problem with their site, but when I use another email server, it works fine. Also, other members of the list have no problems sending email to it.

My ip address is 66.246.75.169; you can see there is a PTR record for it (I've been playing with it, but it's set).

@mwalling:

I personally am going to speculate that the remote site has broken DNS somewhere

@mwalling:

its complaining about what it sees as a lack of PTR records.

I never said you had anything wrong.

@Vance:

You'll probably need to contact the list owner or postmaster at the remote server to figure out what's going on.

There's a reason RFC2821 Section 4.5.1 requires a postmaster email address after all :)

Yes, I understand - but I still wonder if it's on my end.

The problem here is it's on shared hosting, and we have no control over the email server itself. I know the webmaster, but he's not a Linux admin, so he doesn't even know what questions to ask.

The fact that other emails work just makes it seem like I've got something screwed up on my end. I just don't know what it is.

I'll have to see what else I can find. Thanks for the help, everyone.