[exim] Too many concurrent SMTP-Connections

Hello,

I tried google for that problem but it didn't give me any helpfull
hints. I'm running a debian server. About an year after the install it
now begins to bring sometimes the message "421 Too many concurrent SMTP
connections; please try again later"

There are about 5-6 People on that machine that should not be the
problem. I think that might be spamd or clamav because the load with
spams had been increasing.

Or how can I fix that problem?

Thanks,

Martin