Whose email problem is this?

[cleverhandle]

I'm guessing the problem is on their end, but I don't know every intricacy of mail delivery, so I thought I'd check. I was waiting on a registration-confirmation email from a game forum, but it didn't seem to arrive. Sure enough, maillog says:

Jul 15 02:44:51 aristotle sm-mta[5869]: h6F7ipj5005869: ruleset=check_mail, arg1=<nobody@localhost.my.domain>, relay=mail.rpgforums.net [216.82.116.243], reject=553 5.1.8 <nobody@localhost.my.domain>... Domain of sender address nobody@localhost.my.domain does not exist

So obviously Sendmail is upset because it can't verify the sender's name. This is correct, yes? Seems to me like their relay should be rewriting the sender address to ensure a valid hostname. But maybe I'm missing something...

 

[spidey07]

maybe a reverse lookup problem?

meaning nobody.domain.com resolves to 1.2.3.4 and 1.2.3.4 resolves to nobody.domain.com.

'least that's how it should be setup .

 

[cleverhandle]

I don't think that's it. Obviously, "localhost.my.domain" (I wasn't hiding the name or anything) isn't going to resolve in either direction. The machine sending the mail isn't using a valid hostname. So shouldn't their mail relay be rewriting something (the envelope?) to replace "localhost.my.domain" with "mail.rpgforums.net"?

 

[spidey07]

I'm not a mail guy...just a plumber. But weird e-mail problems I look to reverse DNS lookup.

 

[Saltin]

Most mail server's will plug in thier host name in the headers. This can mean you get computername@domain.local, or some other internal namespace that won't resolve on the internet.

It's not uncommon, as Spidey has noted, for mail servers to verify the authenticity of an incoming message by performing a reverse lookup.

It will always fail, of course, if the namespace it tries to resolve is internal. That appears to be the issue.

There is a feature in Exchange, Domino and Groupwise that allows you to overcome this issue.
In Exchange, it's known as the "masquerade domain".

Basically, I tell my email server, with hostname computername.domain.local, to plug in domain.com (a publicly resolveable namespace).

I'm not sure what the feature is called in sendmail, but I'm positive it will have it. All the big mailservers do.

 

[cleverhandle]

Yes, Sendmail does Domain Masquerading also - that's the way I have my mail server setup. Anything that goes out through my server has the domain rewritten. But in this case, I'm on the receiving end. And my server is "playing by the rules", is it not? Even if I were to add rules in sendmail.cf to rewrite incoming bogus domains to some real domain, the reverse lookup would still fail because the IP's wouldn't match. So the only way for me to receive mail such as the above would be to configure Sendmail to not do reverse lookups at all, which is presumably a bad idea.

 

[Saltin]

So screw em. Email server admin's should know enough to ensure thier mail is going to pass the reverse lookup.

Most major mail servers don't parse HOST files, but maybe sendmail has an option to do that ( I don't know Sendmail that well). That's all I can think of.

 

[cleverhandle]

Originally posted by: Saltin
So screw em. Email server admin's should know enough to ensure their mail is going to pass the reverse lookup.

Yes, that was my initial reaction as well. Just wanted to make sure I wasn't missing something on my end. Thanks both of you for the input.