unable to sendmail to different systems

[jagdeesh]

Hi,
I configured sendmail without DNS and i am able to send mail to different users in the same system. but when i send the mail to different system in the same subnet, it gives ...
"#host name
drsn3
#sendmail -v root@drsn4
Hello! This is test mail. Please ignore it.
root@drsn4... Connecting to drsn4 via esmtp...
220 drsn4 ESMTP Sendmail 8.9.3/8.9.3; Fri, 2 May 2003 17:45:42 +0530 (IST)
>>> EHLO drsn3.
250-drsn4 Hello root@hydrsns3 [97.254.0.13], pleased to meet you
250-EXPN
250-VERB
250-8BITMIME
250-SIZE
250-DSN
250-ONEX
250-ETRN
250-XUSR
250 HELP
>>> MAIL From: SIZE=45
451 ... Sender domain must resolve
root@hydrsns4... Deferred: 451 ... Sender domain must resolve
Closing connection to drsn4
>>> QUIT
221 drsn4 closing connection"

hosts file having both the system entries.sendmail.cw file having entries of both the systems. i am unable to locate the problem. Can any one help me...???

Thanks in advance.
Jags.

[Steven E. Protter]

Your machine is not resolving the domain name of the mail recipient.

The domain on systems can and should be set in /etc/rc.config.d/netconf

If there are actual differences, then domain must be resolved.

check /etc/nsswitch.conf for hosts and make sure DNS resolve is enabled.

Check /etc/resolv.conf and see if the entries are valid and can be reached.

run an nslookup and see if DNS is actually working.

If you are an /etc/hosts shop you should have the first entry for machines there be the fully qualified domain name of the machines.

ie server jufprod is jufprod.juf.net

etc

SEP

[jagdeesh]

Hello,
I am not usin DNS at all. nsswitch.conf havinf files in hosts and aliases fields. Both the systems are able to resolve each other when i do nslookup.
Here drsn3 was configured where as in drsn4,i didn't do any changes. Do i need to configure sendmail in drsn4 too..??? i am using domain shortnames. in sendmail.cw fiel(of drsn3) i mentioned both host names like..

drsn3.
drsn4.

and in hosts file these name i added as aliases to the respective hosts.

[Geoff Wild]

It's partly to do with the anti-spam features in sendmail:

Sender domain must resolve

You need to provide a valid domain name - drsn3 is not known to the receving system. Make it something like drsn3.internal.net and make sure that it exists in /etc/hosts on all machines with the name and alias - are both systems configured the same for sendmail? That is with out DNS?

Yu could try adding a DM macro to your sendmail.cf:

DMinternel.net

Remember - that "The remote hostname claimed in the HELO SMTP line is compared to the canonical name. If they differ, sendmail complains."

RGds...Geoff

[Michael Burbury]

Also, don't forget, the receiving node of the email "drsn4" also needs to resole the name of the sending node "drns3", so go to the other system and make sure the name is also in the hosts file (IE: both nodes must be able to resolve each other's name).

Cheers...

[Steven E. Protter]

It is possible to configure the receiving mail server to require dns resolution for all incoming mail.

This is the standard now and it is supposed to stop spam. A lot of spammers send from cable modems and IP addresses that won't resolve. The way to stop that is to require DNS resolution on all incoming mail.

That is what is happening to you.

So, your sending server even if its not using DNS needs to resolve on the reciving server. Or, you can turn off this feature in sendmail.mc Its well documented. I would not turn off the feature unless you have a firewall between you and the public Internet.

http://www.isnamerica.com
Steven E. Protter