my smtp server is very slow to accept connections today

[Paul Howarth]

Don Russell wrote:
> I'm using FC5 and have the "nightly yum update" turned on.
> 
> My FC5 box runs a mail server.
> 
> Yesterday, there were no problems.
> Today, I can't send mail from PCs on the network... the Thunderbird client
> says "Connected to 10...." and eventuaally times out.
> 
>>From external machines I can telnet to port 25 and it takes anywhere from
> 40-80 seconds to get a reply from the server.
> 
> If I'm on the same machine as the server, the connection is immediate.
> 
> That tells me it is not smtp that's slow, but something relating to
> external connections.
> 
> I have not changed any configurations... but with the nightly updates,
> what could account for introducing such a delay?
> 
> I'm thinking somethin like it's trying to a reverse dns look up to check
> the address connecting, and that's taking a long time?
> 
> Any ideas/suggestions?

Check that your nsswitch.conf has an appropriate hosts entry.

Check that /etc/resolv.conf points to nameservers that are working.

Try using "dig" to check them out, e.g.

$ dig @first.name.server -x 212.56.100.58

See how long the lookups take.

Paul.