nsswitch.conf and sendmail

[Don Bentz]

I have a Smart relay host that is used to return mail I send to addresses on the internet. I have made a copy of /etc/nsswitch.conf specifying "dns" as a secondary resolver method. When I merely commented out the IP address of the Smart relay host and restarted sendmail, I got a message saying the "Sender domain must exist". Uncommenting the entry in /etc/hosts resolved the problem. The error message appears to be coming from this line in sendmail.cf:
R $* $#error $@ 5.1.8 $: "501 Sender domain must exist". Question 1). If I simply "install" the new version of the nsswitch.conf without otherwise altering /etc/hosts, my system should still find everything utilizing /etc/hosts unless the servername being searched for is not there, right? Question 2). As long as the Smart Relay can be resolved on our DNS server, I should then be able to comment out its entry in /etc/hosts and avoid the "Sender domain must exist" error, right?

[Geoff Wild · Accepted solution]

1 - correct

2 - correct

caveat - DNS must be functioning for the above to work.

Also, remember to stop/start sendmail after making changes.

Because you are using a SmartRelay, I would also add your domain to the DM macro in sendmail.cf:

DMyourdomain.com

Rgds...Geoff

[Don Bentz]

Thanks Jeff. Anybody(?). Regarding the first part of the problem - "Sender domain must exist", the problem I am now having seems to be that when I use DNS to resolve the IP address of the "Smart Relay", it returns the following: "May 28 12:30:13 hpopsnew sendmail[24052]: MAA24052: ruleset=check_mail, arg1=, relay=[135.10.11.90], reject=501 Sender domain must exist". The relay IP address is our "intranet" IP for the Smart Relay host (fc.xxxx.com), but not the "internet" IP address for that server, known as fc.xxxx.com. I don't understand where it got this IP address from (in the relay=[135.10.11.90]). I was advised by somebody to insure that the DNS admin added an MX (Mail Exchanger?) record for that (135.10.11.90) address with the fc.xxxx.com "Friendly name" to the DNS server. Any comment about this?