On 20 Dec 2023 16:14 +0100, from m...@dorfdsl.de (Marco Moock): >> I have heard that there is a countermeasure against spam run be big >> mail providers by rejecting the first contact by SMTP and accepting >> the next contact. Most spammers seem to try just once. > > Do they reject with 5xx or 4xx?
I suspect that is in reference to greylisting, in which case it absolutely should be a 4xx temporary reject. The idea being that legitimate SMTP clients will retry later in response to a 4xx. Though big providers have probably moved on toward making decisions based on IP reputation rather than whether some system retries after some indeterminable delay. -- Michael Kjörling 🔗 https://michael.kjorling.se “Remember when, on the Internet, nobody cared that you were a dog?”
