[Exim] SMTP conections rejected

I am currently running Exim 3.35 on Debian. Periodically my SMTP gateways
will stop accepting SMTP connections. If I telnet to port 25, I get the
following message:
telnet: Unable to connect to remote host: Connection refused.

It appears that this happens each time the queue runner process begins. I
added the following lines, and tried changing the retry rules.

smtp_accept_max = 150
smtp_accept_reserve = 40
smtp_reserve_hosts = 10.0.0.0/16

None of this appears to have changed anything. SMTP connections continue to
be refused several times an hour. Is there something that I am missing
here?

I am planning to upgrade to Exim 4, but would like to make sure I have a
solid configuration before attempting the upgrade. Thanks for your help.

Chad Butler