On 2020-09-23 12:15, terryc wrote:

> The norm seems to be to just accept everything and process it, but
> until recently, all my internet services cam with a data charge. So for
> our domain, the easiest & cheapest method is just to block known
> spammers and not pay data charges.

Much depends on what you mean by "block".

You can reject connections from known spammer IPs at the IP level via
iptables or via tcpwrappers. You can also reject _delivery_ of messages
at the SMTP level with a 400 or worse status code. But once you accept a
message with a success status after the DATA stage, you are obliged to
either really deliver it or else bounce it back. It is not acceptable to
send messages down a "black hole".

> FWIW, I do not accept email by IPv6.

I am interested to know the specific reason for this. You know that the
RBLs do list IPv6 addresses, right? In fact, I just enabled IPv6 in my
own mail server a couple of days ago, and voila I ended up in zen (not
having done all of my homework).

--
Ian