[Exim] Long delay in initial exim response

I'm running exim v3.13 on Solaris 7 (with fairly recent patchs).

Every so often exim takes several minutes in responding to all new
connections.

exiwhat shows that an exim process has been forked to handle the
connection but that process then takes a while before it returns the
initial response. Once a response has been sent there doesn't appear to
be any delays in handling the rest of the transaction.

This even occurs if I do 'telnet localhost 25', and sometimes the
connection times out!

This has also happened on older versions of exim and Solaris.

The problam can last several hours and then everything is back to normal
(until the next time)

Other systems on the network running exim don't have the same problem
only the main mail server (typical!)

Any help would be much appreciated.

--Terry Edhouse
Department of Electronics
University of York