[exim] How to disable Clamav for some hosts

Hello,

I would like emails sent by some hosts to don't been checked
by clamav.

Actually I tried to add before the line "malware = *" :
  accept
    hosts = a.a.a.a:b.b.b.b:c.c.c.c

But it seems to doesn't works. Is there a "good" way to do this ?

Thanks,
Olivier