I have a problem that dates back now several version of SM related to spam filtering, where certain domains or even individual email accounts seem to have no or little spam filter applied. Yes, I've checked and they are not exempt from any settings or bypassing spam filtering. We have implemented Bruce's excellent recommended spam settings. Most clients are not being bombarded by spam, but a couple are being buried. Greylisting is in effect and not being bypassed for the domain.
One domain/user in particular seems to have no filtering being applied. Looking at random spam headers, some have a SmarterMail spam weight of 10-12; other very obvious spam messages have none.
One or two versions ago I opened a ticket related to this but there was no resolution really.
My question is whether it's possible for the filtering process to somehow bypass a domain due to a bad configuration file or any other explanation.
Or is it as simple as those users' email address are just being bombarded more than others so the percentage getting through is the same, but volume is higher?
I appreciate any thoughts or help.