sendmail dns config question - SendMail

On Sat, 23 Dec 2006, in the Usenet newsgroup comp.mail.sendmail, in article
<U--dnZUAc-Rm9BDYnZ2dnUVZ_tadnZ2d@comcast.com>, dansawyeror wrote:

>#nslookup domain; sendmail -v -q
>
>After executing this command the e-mail was sent. This apparently
>populated a cache that allowed sendmail to resolve the address. What is
>the cache?

Not quite enough information - but what happens if you try to 'ping'
the domain? Does the name resolve? If _NOT_ then what does the files
/etc/host.conf and /etc/nsswitch.conf look like? Do they have a line
that contains the word 'host'?

[compton ~]$ grep host /etc/host.conf /etc/nsswitch.conf
/etc/host.confrder hosts,bind
/etc/nsswitch.conf:hosts: files nis dns
[compton ~]$

Explanation: 'nslookup' (and 'dig', and 'dnsquery' and 'host') are DNS
query tools that are solely used to query a DNS server. The normal
hostname lookup is run by a function in the C library, and this function
looks at one or the other of those files to see where it should try to
find the hostname:IPaddress data. The entries above tell the resolver to
look first in the /etc/hosts file (hosts or file), and if that fails, to
look elsewhere - eventually looking at nameserver data (bind or dns).

The DNS query tools ignore these files, because their job is to query
the name servers listed in /etc/resolv.conf (or the one on localhost if
no 'nameserver' line is in resolv.conf).

Old guy