sendmail sending slowdown

[Bob Chiodini]

Andy Green wrote:
> Somebody in the thread at some point said:
>   
>> Suddenly (starting yesterday) my mailserver is very slow when I send mail
>> through it.
>>
>> I cranked up ettercap on the server to watch what's going on, and it connects
>> immediately when I send mail, but just sits there for between ten and thirty
>> seconds before it finally accepts the mail for sending.
>>     
>
> On the server, what is in /etc/resolv.conf?  What happens if you ssh
> into the server and try to do, eg
>
> dig <sending client ip>@<nameserver ip in server /etc/resolv.conf>
>
> for example
>
> dig 192.168.0.10 at 123.123.123.123
>
> and how fast does it come back with a reply?
>
> Are you using a realtime blackhole for lookup?  Maybe that is slow.
>
> -Andy
>
>   
/etc/nsswitch.conf governs the lookup order.  The FC6 config was files 
then DNS, but I've seen other distros that had DNS prioritized over 
/etc/hosts.

Two other things come to mind:  IPv6.  There was a discussion recently 
how to turn off IPv6 in F7 or maybe something is amiss with an upstream 
nameserver.

I'm not familiar with ethercap, but is anything else going on 
network-wise while sendmail is sitting there?  There is also a debugging 
mode for sendmail, plus /var/log/maillog might tell you something.

Bob...