I personally do spam filtering for our site. Actually, it's not "spam"
filtering per se. If you don't have a domain in the from addr which resolves,
your mail is rejected. If you are not a customer of ours and try to relay mail
off our servers, your mail is rejected.
This to me seems completely just. Why should you send mail with a false return
to address and why if you are not my customer should you send mail?
Now, filtering based on hostname & blackholing is a bit extreme. It limits the
user's right to choose. As long as the commercial soliciter has a valid
reply-to address which you can use to bitch and complain, then I feel it's
fine.
However, I believe repeated unsolicited commercial email is harassment. For the
same reason you can't call a person on the phone in the US 4 or 5 times
unsolicited (it's against the law last I checked). It's wasting my time. On the
Internet, it's wasting my bandwidth and resources.
Does anyone have any stats on what percentage of networks is spam? I figure
probably around 5%.
Jordan
I personally do spam filtering for our site. Actually, it's not "spam"
filtering per se. If you don't have a domain in the from addr which resolves,
your mail is rejected. If you are not a customer of ours and try to relay mail
off our servers, your mail is rejected.
This to me seems completely just. Why should you send mail with a false return
to address and why if you are not my customer should you send mail?
These are standard features to most sendmail anti-spam/anti-relay patch
sets. Now, what about blocking mail if it's passed to you by a host that
has no in-addr.arpa record? I've recently started doing this on a few
systems since I've found that some spam providers (either because they
move too frequently, don't want to be resolved, or just don't have a clue)
don't have reverse DNS.
I'm blocking several hundred messgaes/day per system and get log entries
such as:
sendmail[1725]: Ruleset check_relay ([207.199.68.35], 207.199.68.35)
rejection: 418 obtain a hostname
So far, I've gotten no complaints, so I assume nearly all the mail that
can't get in is junk mail.
Now, filtering based on hostname & blackholing is a bit extreme. It limits the
user's right to choose. As long as the commercial soliciter has a valid
reply-to address which you can use to bitch and complain, then I feel it's
fine.
What about valid (i.e. resolvable) from addresses that are invalid for
mail delivery? i.e. if you get a lot of spam, surely you've gotten
messages from who knows where, claiming From addresses like
897632@aol.com. Sendmail rules will resolve that, but email a complaint
there, and it's likely to bounce. I've not figured out a sendmail rule
for blocking such mail from: addresses.