Re: lists

[Michael Kjörling <2695bd53d63c@ewoof.net>]

On 20 Dec 2023 16:14 +0100, from mm@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?”