On 4/6/20 1:16 PM, Michael Orlitzky wrote:
Greylisting suffers from one problem that unplugging the server doesn't: greylisting usually works on a triple like (IP address, sender, recipient), and can therefore continue to reject people who do retry, but retry from a different IP address. This occasionally affects things like Github notifications and requires manual intervention.
I used to be a strong advocate of greylisting. I had some of the problems that have been described. Then I switched to Nolisting, a close varient of greylisting that I haven't seen any of the same (or any) problems with.
If a sending email server follows the RFCs and tries multiple MXs, then email gets through in seconds instead of having to re-try and wait for a greylist timeout.
There's also no issue with (re)trying from different IPs.
(I would still recommend greylisting, personally, but it's a harder sell than that of foregoing a secondary MX.)
Greylisting, or better, nolisting is a very good thing. See my other email for why I disagree about foregoing additional MXs. -- Grant. . . . unix || die
