Any smart spammer will just tweak his spam to not hit these rules... And if he hasn't, it's because the vast majority of people don't use SpamAssassin
Any smart spammer will just tweak his spam to not hit these rules... And if he hasn't, it's because the vast majority of people don't use SpamAssassin
Well-known rules will block most spam, some with occasional collateral damage but many with no realistic chance of collateral damage.
Entity-encoding @ as @ in email addresses in HTML will block the vast majority of email address harvesters, with no collateral damage.
Adding a honeypot field to an HTML form, with the label “If you are human, leave this field blank” and hidden by CSS, will catch practically all spam submissions, with no collateral damage.
I am sure there are plenty of smart spammers, but it also seems like a lot of spam comes from folks using scripts and email lists they use without fully understanding. It appears SpamAssassin would help with those operations.
So I wasn’t expecting Postgrey to provide much benefit. As it happens, in 10 years of running my own mail server, it’s the only anti-spam measure I’ve had to bother with.
Spam is all about high-volume/~no-cost delivery of crap. Time spent tweaking the spam - to evade $Defense_1, $Defense_2, etc. - is added cost. Especially if $Defense_n is only used by a few of the prospective victims (folks too savvy or paranoid to be suckered do not count), then tweaking to get around $Defense_n is a losing strategy for the spammer.
Bingo. Not that there aren't a lot of people running SA, but spammers want to be able to deliver to the big players(1) (gmail, o365, etc), not the size folks out there running SA. It's not worth their time to devote effort to optimizing for a rounding error in the deliverability equation.
(1) Unless they're selling 'targeting' services where you're paying to deliver to a specific domain/user which might be behind SA. Plenty do, but that's a little bit farther down the criminality spectrum and vastly less volume than shilling peener pills or warranty extension scams.
edit: formatting