I'm getting the following error:

> ----- The following addresses had permanent fatal errors -----
> name@isp.net
> (reason: 553 ns1.domain.com does not exist)
>
> ----- Transcript of session follows -----
> ... while talking to mail.isp.net.:
> >>> MAIL From:<apache@ns1.domain.com> SIZE=909
> <<< 553 ns1.domain.com does not exist
> 501 5.6.0 name@isp.net... Data format error

This only happens when sending to addresses of a few select ISPs. It seems that these particular ISPs do a more thorough check of the sending mailer. Most other destinations work fine.

I imagine that this is a setup issue with sendmail. Does anyone have an idea of what's going on and how I can fix this? I've got a Redhat 7.1 box and I usually use Webmin for administration stuff.

Thanks.

It has to do with your sending emails from a domain that can't be resolved by the receiving sendmails.

For instance a bogus domain name (needs to be fully canonical), or you do have a valid domain name but only rely on aliasing, you don't have a n "A" entry in your zone config.

Well, I guess more info about your config. may help.

Originally posted by cyansmoker
It has to do with your sending emails from a domain that can't be resolved by the receiving sendmails. Why can't it be resolved? The domain name in question is both the name of my box and the name of my domain name server. Seems like it should be resolvable.

For instance a bogus domain name (needs to be fully canonical), or you do have a valid domain name but only rely on aliasing, you don't have an "A" entry in your zone config. Well, I have an "A" record for domain.com, but not for ns1.domain.com. Does it actually NEED one??

Furthermore, I'm not even trying to send from domain.com, but rather from anotherdomain.com, which is a valid domain name, with an "A" record and so on.

Well, I guess more info about your config. may help. What else do you need to know?

BTW - I'm using the mail() function in a PHP script. This shouldn't make a difference - or should it? Perhaps I need to change something in my PHP configuration?

Thanks for the help. I'm sure that I'll kick myself when I realize what I'm doing wrong.

From the top of my head, your emails must be originating from your host in a non-equivoque manner: all the fields in your mail headers must point to this domain, and it's a possibility that the remote sendmails also try to reverse your IP to this domain.
More likely: do you have an MX entry for this domain that actually points to an actual 'A' entry and not an aliases such as 'mail.yourdomain.com. CNAME whatever.com.' and then an 'MX xx mail.yourdomain.com.' => this may be a problem.

-Chris.

Umm, thanks cyansmoker. Ya' know, I hate it when I'm stupid. Or, at least I feel stupid, since I didn't understand one word of your last post.

Let's try another angle... There are a number of items that can be configured... masquerading, trusted users, outgoing domains, outgoing addresses, and so on. Perhaps one of these might be the answer I'm looking for? I can't even figure out what they're for.

Thanks

Well,
all these options end up in config. files; are you modifying them through a UI, such as webmin?

Could you write here your DNS configuration regarding the domain supposed to be sending these messages?

cyansmoker,

Thanks for the help. I sent a link of this thread to my ded server provider, and he picked up on the "A" record. He noticed that I didn't have one for ns1.domain.com.

I'm not kicking myself, but I'm not exactly pinning medals to my chest either. :-)

Thanks again for the assistance. Everything works as it should now.