Turns out greylisting is awesome
I used to get several hundred spam emails a day on micropipes.com. I wasn’t thrilled with having a four or five digit message count in my spam folder, but I deleted the few that slipped through each day and didn’t think about it much more. Someone else running a domain on this server got enough initiative to do something about it though and installed a Grey Listing filter.
For those who are unfamiliar, from the site:
What happen is that each time a given mailbox receives an email from an unknown contact (ip), that mail is rejected with a “try again later”-message (This happens at the SMTP layer and is transparent to the end user). This, in the short run, means that all mail gets delayed at least until the sender tries again - but this is where spam loses out! Most spam is not sent out using RFC compliant MTAs; the spamming software will not try again later.
It means a short delay to get a message from someone that has never mailed you before, but subsequent messages are delivered immediately and the amount of spam I get is nearly nothing now - I’m averaging about one per day. Definitely a win if you’re fighting a flood of spam.