[exim] Delaying in answering incoming SMTP

Hey everyone,

One of the mail servers I've got here seems to take a while to initiate
incoming connections on port 25 when load gets even a little bit high.

When the load is low (<10) I can expect to telnet to my mailserver on port
25 and see the connection opened and the exim smtp banner near
instananeously.

However, when the load gets above 10, which it does frequently, we can
expect to wait anywhere between 1-5 seconds for the connection to be opened
and the banner to display.

This is causing some of my users trouble with their clients timing out and
it's also causing me to receive a ton of notifications from Nagios claiming
there's a problem.

Is there anything I can do to speed this up? I'm working on sourcing another
processor for the box and that should hopefully pick up the pace a little
bit but I'm concerned more with short term.

Much appreciation to everyone.

Justin G.