[exim] usage of smtp_reserve_hosts

(sorry, if posted twice)

Hi list,

if i define a hostlist for "smtp_reserve_hosts", how often is this file
read by the smtp-listening-daemon? Only once after start or every time a
connection arrives?

Background: i try to make this list dynamic, based on the ip's of hosts
which have send mail authorized in the last e.g. 4 hours, to have a pool
of free smtp-slots for our customers, regardless if our servers are
flooded with connection-attempts by botnets.

Should i send a SIGHUP to the listener every time the list has changed?

Regards
Marian Neubert