On 25/10/18 07:33, Viktor Dukhovni wrote:
> On Thu, Oct 25, 2018 at 08:11:35AM +0200, Poliman - Serwis wrote:
>
>> Hi. I heard that having a non-functional server as the primary MX is a
>> well-known trick to reduce the amount of incoming spam, as most software
>> used by spammers will only ever try the highest-priority MX. How to do this?
>
> No. This is a myth, and reduces the reliability and performance
> of legitimate email delivery. Use a decent RBL, postscreen(8) may
> help to reduce the load on the server and keep smtpd(8) more available
> for legitimate email.
>
Yesterday, my Postscreen blocked 92 percent of incoming connection attempts:-
POSTSCREEN ATTRITION REPORT FOR Wed 24 Oct 2018
Connections to Postscreen - IPv6: 28
IPv4: 395
Individual hosts: 105
Misc disconnections 392
Black-listed Locally: 100
Black-listed by DNSBL: 392
Pre-greets: 13
Hang-ups: 11
Command Pipelining: 1
White-listed: 30
PASSed by PostScreen: 1
New: 1
Refusal Ratio: 92 percent
There are some anti-spam projects which offer MXes for your use.
You set one up with the LOWEST prioity (your "MX of last resort"); If a message
reaches it, the MX will collect stats
and then return a TEMPFAIL.
Legitimate mail would not be affected as a retry will be forced, though you may
want to find out what the project does
with the stats they collect.
I think Project Honeypot does one, though they are more interested in Web
decoys.
Hope this helps
Allen C
