[Exim] Child processes

Hi,

I am suddenly getting a large number of error messages in
the panic log which are as follows:

"1999-08-17 16:29:08 11Gk7Y-0008Kz-00 Process 32063 (parent 1) failed to
create child process to send failure message"

It is a busy mail server running exim-3.02.
smtp_accept_max is set to 500, but this problem started to occur at round
about 300 incoming connections.

What should be done to try and stop this from happening ?
The machine itself is idling.

Thanks,
Warren