[plug] Blacklisted mail server?

[Ben Jensz]

To quote Wietse - "Junk mail is war, RFC's do not apply". 

It can be useful to drop known "bad" client IPs before they get to the 
actual SMTP service, as then it uses less resources on your mail server 
systems as you don't have the overhead of having used up one available 
SMTP connection to a host that you're only going to tell to sod off 
anyway.  Considerations such as this do come into play when you're 
dealing with large volumes of email like ISP's do.

That said, there have been issues with the Sorb's DUL list during the 
last week, which have lead to ranges being incorrectly listed.  So 
actively giving a reject response (rather than just dropping the 
connection outright) does at least give the sending client an indication 
as to what is wrong.


/ Ben


Mike Holland wrote:
>
> Isn't that just plain wrong?  Both with internet protocol standards, 
> and ethics.
>   They should give an error message with explanation first. e.g. 
> postfix says:
>
> 554 Service unavailable; Client host [xxx.xxx] blocked using
> >     dul.dnsbl.sorbs.net; Dynamic IP Addresses See:
> >     http://www.sorbs.net/lookup.shtml?[xxx.xxx]
>
> So at least the poor guys know whats happening.
>