1 minute pause on sendmail login

[Les Mikesell]

On Wed, 2005-12-21 at 16:57, Andy Pieters wrote:
> Hi list
> 
> I am seeing extreemly long login times on my smtp server.  It pauses for ~1min 
> right after connection.
> 
> telnet mail.vlaamse-kern.com 25
> Connected to mail.vlaamse-kern.com 
> Escape character is '^]'.
> ****PAUSES FOR 1 MINUTE***
> 220 mail.vlaamse-kern.com ESMTP Sendmail 8.13.1/8.13.1; Wed, 21 Dec 
> 2005 18:38:21 +0100
> 
> Further information: when I connect from the lan to port 25 on the public ip 
> address, the connection is refused, but when I connect from the lan to port 
> 25 on the server's private ip address, the connection is established and the 
> pause does not occur.
> 
> Can anyone make sense of this?

Sendmail will do a reverse DNS lookup for the IP address of the
connection to put the name in the logs.  Apparently this
doesn't work for the address you are testing from and you
wait for a timeout.  Perhaps the delegated DNS server is
blocked by a firewall that drops the packets.  Likewise there
is an IDENT query for the owner of the socket, but those
timeouts are usually faster.

-- 
  Les Mikesell
   lesmikesell at gmail.com