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List:       postfix-users
Subject:    Re: Preferred/maintained greylisting options?
From:       " () lbutlr" <kremels () kreme ! com>
Date:       2020-05-24 15:09:05
Message-ID: 18BC362E-5BAD-44CD-8BCB-7EB4DF3A845D () kreme ! com
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On 21 May 2020, at 12:49, Charles Sprickman <css@morefoo.com> wrote:
> I was wondering if greylisting might be a good option here.

It's a matter of how much Nanking you are willing to do and how much legitimate mail \
your are willing to lose.

The usual method of greylisting where you tell a server to try again later (4xx \
error) will cost you legitimate mail as many senders, including very large senders, \
will retry from different servers (google, Amazon). Others, in the idiotic belief \
they are being "secure", will never retry. Many of the latter are banks.

Other forms off greylisting, like slowing the connection rate and making the \
transaction take a bit longer than usual are far more effective and less likely to \
cause issues with legitimate senders.

Greylosting also really screws up the "authenticate your email right now. No, right \
this second. We sent you the code, enter it now in the next ten seconds or we delete \
your account and ban your IP" idiocy on the web that, nonetheless, some of us are \
forced to deal with. It's impossible to keep up with the list of domains doing that, \
especially when most of the verification emails originate from other servers.

Postscreen, out-of-the-box, works exceptionally well and blocks more spam than any \
thing else I've used. Sure, I run SpamAssassin as well, but it sees very little use.

Add an RBL or two, and it's kind of like magic.


-- 
Knowledge equals power... --... Power equals energy... People were
	stupid, sometimes. They thought the Library was a dangerous place
	because of all the magical books, which was true enough, but what
	made it really one of the most dangerous places there could ever
	be was the simple fact that it was a library. Energy equals
	matter... --... Matter equals mass. And mass distorts space. It
	distorts it into polyfractal L-Space. --Guards! Guards!


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