I discovered this after Postfix had crashed under the weight of spam a machine on my ISP's local subnet was sending through me.
The fix is to change
mynetworks_style
from the default of subnet
to host
. You do use authenticated sending only, right? (check smtpd_recipient_restrictions
includes permit_sasl_authenticated
and not a lot else).I debugged this and was up to 2am last night clearing up after the mess.