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Old 12-26-2003, 03:46 PM   #1
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Registered: Dec 2003
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Strange sendmail problem


The following problem is driving me nuts. I have setup a RH8 server with sendmail running. It has been setup in a small network, default gateway is

a) Sending mail to local users -> no problem.

b) Sending mail to external users (valid email address like -> mail is rejected, errror:

----- The following addresses had permanent fatal errors -----
(reason: 553 <root@localhost.localdomain> unable to verify address)

c) Sending mail to a valid hotmail account (e.g. -> success, mail is delivered without problem!!

Why is c) working and b) not? What is wrong in the setup?
I can ping any address in the outside world and also nslookup works fine.
E.g. nslookup -silent www-hccnet-nl gives:

Non-authoritative answer:
Name: www-hccnet-nl

Old 12-26-2003, 04:09 PM   #2
Registered: Sep 2003
Location: Washington State
Distribution: SuSE 8.0, SuSE 9.0, Slack 9.1
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Most e-mail servers do a DNS look up on the sending domain before the accept any e-mails. A lot of the popular pop3 providers (such as hotmail) don't bother becasue it's primarily a spam reducing effort.

Basicaly, the recieving server is trying to do a DNS lookup on localhost.localdomain and not getting anything. To solve it, I guess change your domain to something that's resolvable, or tell sendmail to send things from addresses like root@ (Please note this is a random IP address)

Unforutnately, I don't know the mechanics of the change, so I can't help you there. Hopefully what I did say helps you understand what's up at least.

Old 12-26-2003, 04:38 PM   #3
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Thanks Derek,

At least I have an idea what is going on. Point is that I am running this server from my homeplace. I have an ADSL connection (with a fixed IP address) but no 'official' hostname. So I guess I have to change the sendmail config. Anybody having an idea?

Thanks, Theo M.
Old 12-27-2003, 02:53 AM   #4
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Registered: Nov 2001
Location: Budapest, Hungary
Distribution: SuSE 6.4-11.3, Dsl linux, FreeBSD 4.3-6.2, Mandrake 8.2, Redhat, UHU, Debian Etch
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The best is to get an own domain name.
If it is not possible, you might try to use your ISP's mail server to send your mails.

If you insist on sending mails by your own mailserver, setting up sendmail to use features masquerade_envelope and masquerade_all, and specifying a real domain as the masquerade domain might help.

Say, if you have an email address at your ISP: someone@your.isp, then you can
setup sendmail to masquerade all mails as if sent by domain "your.isp".

However, you might still have problems, since domain "your.isp" does not resolve to your IP address. If so, you may try to set sendmail to relay mails through your ISP's mail relay by setting smart_relay_host to your ISP's smtp server.
However, you may still have problems, if your ISP's smtp server is not willing to relay your mails...

Last edited by J_Szucs; 12-27-2003 at 03:07 AM.


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