DragonFly kernel List (threaded) for 2004-01
Spam issues in DFly lists
This is just a head's up... the command channel for some of the
dragonfly lists is starting to get random spam.
It's probably just a matter of time before the posting channel starts to
get it, at which point I will have to turn the spam filter on for the
I am going to try to avoid turning on the 'only a subscriber can post'
feature of the list server, because I think it's anti-social, but
the filter I will use does a number of checks.
To test whether the spam filter would block your emails, simply send an
email to test@xxxxxxxxxxxxxx This goes into a sink/null so you will not
get a reply. If you do not get a bounce you are ok. If you do get a
bounce then the spam filter has got you by the throat :-).
Basically the spam filter requires:
* Reverse DNS must resolve.
* Reverse cannot resolve to a cablemodem or DSL domain name
(I do this with a wildcard compare against ISP's that I get
If you have your own personal domain and the reverse points to
it, you should be fine.
If you get a bounce due to this, you should be able to send mail
by pointing your SMTP to your ISP's SMTP server instead of
trying to make direct connections to the target domain.
If that bounces I can probably adjust my list to compensate,
unless the ISP is the source of a huge amount of spam sent
through its own servers.
* Envelope from address must resolve. The spam filter makes a
reverse connection (as if it were sending mail back to the From
address) to test the address. If the RCPT succeeds it's happy,
if it doesn't, the mail is rejected. No actual email is sent,
it RSET's the connection after testing the address.
The filter gets about 80% of the spam that comes into my other domains
and is fairly non-intrusive except for the occassional person who is
trying to run a personal SMTP server off their dsl or cablemodem line
without setting it up to forward to their ISP's mail server.