[lug] Wierd Sendmail vs resolv.conf issue.

[Nate Duehr]

DNS lookups are a blocking operation as written into many programs, can
you actually do a dig from the mail machine to the DNS server that
you're adding to the /etc/resolv.conf file?

i.e.:  dig @IP.OF.DNS.SERVER www.yahoo.com

... and get a response?

If not, adding that server to /etc/resolv.conf will cause you problems.

At the new site, is there a firewall between you and the remote DNS
server?  Stuff like that...

gethostbyaddr is going to do a REVERSE lookup.  Is your sendmail trying
to reverse resolve itself or other nameservers?  Are there actually
reverse records in the reverse zones for the new site?

Just brainstorming -- without more details I can't do much but guess.

On Thu, Apr 05, 2001 at 01:18:12AM -0600, John Starkey wrote:
> > By leaving out the namserver entries in /etc/resolv.conf , you will default
> > all of your name server lookups to localhost (127.0.0.1). So before you do
> > this, be certain you actually have a nameserver running on your localhost.
> 
> It's a virtual server Yeah. They're running BIND. But why *adding* the
> nameserver line is gonna choke sendmail is a mystery.
> 
> > What are the failure messages? (Your logs should tell you why sendmail is
> > bouncing the mail.)
> 
> >From the logs:
> 
> Host unknown (Unknown error: 275)
> gethostbyaddr(161.58.xxx.xxx) failed: -1
> alias database /etc/aliases.db out of date
> 
> But aliases.db being out of date is something i don't get either. It's not
> showing up in the logs now, they rehashed it.  But "gethostbyaddr(xx.xx.xx.xx)
> failed" is. And mail is delivering fine. There is an old /etc/resolv.conf that
> contains the old entries.
> 
> > Does an nslookup return the expected MX records for the domains ? (Try
> > nslookup both on your localhost and to one of your external nameserver
> > entries).
> 
> I tried it from several DNS including the SOA and localhost and everything
> resolved fine. MX was there. No problems. It was getting to the server and
> confirmed by the logs.
> 
> 
> 
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-- 
Nate Duehr <nate at natetech.com>

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