[exim] unexpected error

Hi

Since last night i have problem: in my exim log i have many times insert
something like:

unexpected disconnection while reading SMTP command from .... Connection
reset by peer. Servers adressess are differents.

At this time count of connections to my server increased and exim writes
in logs: refused: too many connections
although i increased count of smtp connections from 50 to 800

Help me, please! Regards!