Sendmail and dns suddenly quit talking

[Mike Smith_33]

I have a two node, hp 11.11 serviceguard cluster that started having problems with mail sometime late 8/4/2006 or early 8/5/2006. I was able to determine that remote email addresses are going but addresses to my company domain go into the mail queue and either show up hours late or never.

After much viewing of syslog.log, mail.log, sendmail.*, etc/hosts etc... and working with two hp support guys their response was, this was a dns problem. We have just gotten a sniffer trace done wherein I sent an email to one internal and one external address at the same time.

What we are seeing is the dns server responds back with about 7 nameservers for the external address and then sends the mx record. The email goes and everyone is happy. For the local domain, dns responds back with about 30 nameservers, then waits to send more data. The mail process is either full or still hasn't seen the mx record so instead of gathering more data it goes to the next dns box and the process repeats.

Here are my issues, these systems were sending mail for close to year with no problems, now neither works correctly. As far as we can tell, neither the systems nor dns were changed recently.

Is there some process buffer that needs to be updated or should dns be queried in a different manner to obtain a more succint listing? Any ideas as to a solution or even what could have caused this would be appreciated.

[IT_2007]

Looks like problem is on DNS server which is not able to send mail. Talk to DNS team and see if they can see any issues on their side since there is no changes happend on your side.

[Mike Smith_33]

I have worked with dns support and they did not change anything either. I have production email that will not flow so I do not have the "not my problem" button to push. I need information like what is sendmail requesting? What format does it expect the response to be in?

[Tim Nelson]

Try to use sendmail -v user@host.mydomain.com to help troubleshoot.

See if the responding mailservers name or IP keeps changing, with 30 to choose from there should not be an issue. Using sendmail in verbose mode may just help you to find where the issue lies.

DNS lookups or mail servers. If DNS is working right you should get an almost immediate response from some mail server. If not it gives you something to chase after.