[Exim] conditional logging

I was logging "smtp_connection" and found it useful to see the number of
active connects. However I have switched on a SMTP health-check which
repeatedly connects and disconnects. I would like to exclude certain IP
numbers from logging e.g.

log_omit_from = 139.133.2.2: 139.133.7.20


Can't see any way to do this in the book but only too aware I may have
missed the section.

John Linn