[jeremyjh]

I do not have any choice at all about what spam filters the recipients of my email may be using. I have never had this problem personally, but there are many, many accounts on webhostingtalk.com of IP ranges being banned Spamhaus without any evidence of spam; of IP addresses that remained banned after ownership changes hands and other problems. There are always two sides in every story. On balance I think Spamhaus is doing a very good and necessary thing. I don't know about this particular case, but I've read accounts of what sound like very reasonable grievances.

[supar]

I've been designing honeypot/traps as triggers for mail filtering infrastructures for years, and this is very hard to automate process. It started like something that you could watch from time to time in the late '90, maybe slab a DNSBL or two, but right now has become a bloody nightmare. I remember when at some point almost everybody started to "reinvent" greylisting out of convergence, even before it was called as such. Reading nanae (via NNTP) was always a good read.

You constantly have to check if there is a chance that spammers noticed your honeypots so that they can avoid them or use them against you as well (the bigger you get the more sophisticated these attackers get too), you have to use tagged email addresses that can be linked back to the offenders. Methods to probe address ranges multiple times before validating them, and ways to automate the unlisting as well. False positives are basically unavoidable at some point, also because spammers themselves like to rotate their addresses based on their previous owners or known datacenters that are "too big to be blocked" wholesale for this exact reason. If they had a chance to know one of your trigger addresses, a common practice is to generate spam from a "safe" range into the trigger address, in an attempt to generate a false positive and thus, of course, backlash. It's sickening.

Exchanging digests of message contents among multiple server cooperatively became a good indicator of spammyness (vipul's razor), though you would catch bulk emails in the process, and spammers quickly adapted to random email contents so that the method became quickly ineffective.

The real problem here is that these assholes don't care as long as they can deliver the message, that's the only metric they have and care for. Maybe you don't care for it, because you can then use filtering later, but that's a huge volume of trash that needs to be shoveled around. I actually witnessed many cases in organizations bigger than a hundred eployees where several servers were used 24/7 just to churn messages through "dspam" or similar filters before delivering to the final mailbox. This is a huge cost in terms of measurable power wasted for a couple of assholes.

[jiggy2011]

I had a similar problem and never found out exactly why it happened.

The hypothesis I came to was that we weren't using SPF records on the domain associated with our IP address for a long time.

Some spammers were taking advantage of this by sending emails from different IP ranges with the From: header spoofed to be from our domain.

So Spamhaus blocked our IP address on the grounds that spam filters would also be able to confidently block anything appearing to originate from a domain name that resolved to our IP address.

[jackalope]

It's extremely unlikely that spoofed headers or the lack of an SPF record would get you listed on an RBL, especially Spamhaus. I can't guess what happened in your case, but somehow your IP address obtained a bad reputation or was unlucky enough to be in a tainted block. FWIW, the very first thing I do after getting an IP allocation is run an RBL check on it and demand a replacement if it's listed anywhere.

[jiggy2011]

Yes, it was a fairly weak hypothesis. OTOH we got on several RBLs a number of times and managed to get taken off them. Once I added an SPF record it hasn't been a problem since.

Didn't use SPF to begin with because there was a large number of hosts legitimately sending mail for the domain and it was a pain to get all of the IP numbers for various crazy reasons.