You seem to have mistaken us for spammers, all our email is opt-in and/or CAN-SPAM compliant. We've even retained a deliverability consultant who certifies that what we do isn't spam.
What exactly do you mean by opt-in?
Unfortunately, the term has wildly different meanings to different people. Then there's "confirmed opt-in" or COI (sometimes called double opt-in), which also means different things depending on who you ask.
For the purposes of this DNSBL, all that matters are our definitions.
When determining whether or not an email is spam, opt-in just doesn't cut it. Opt-in suggests someone gave you an email address. Maybe it was the owner of the address. Maybe it was someone else and they typo'd their address. Maybe it was some random 3rd party making up an address because a web form they were filling out required an address, and they didn't want to put their own in it and risk getting spammed. Maybe someone gave or sold you a list of addresses and said "they're all opt-in"...but opt-in to what?...and what do they mean by opt-in?
If you want not to be treated like a spammer, what you need is COI.
What is COI?...or more importantly, what is our definition of COI?
COI means that after you have an opt-in email address, the first and only email you send to that address (until confirmed) is a confirmation request message. The confirmation request message contains no advertising. It should be as short as is practical. Its sole purpose is to validate the opt-in, i.e. determine that the address is valid and was given to you by a legitimate user of the address. The opt-in is then confirmed by the recipient of the confirmation request message doing something in response to the confirmation request. This could be an email reply to the confirmation request (which would have to have contained some "unique cookie" so that you know the reply did in fact come from the same person who received the confirmation request) or visiting a unique URL contained in the confirmation request.
If the opt-in is not confirmed as decribed above, how do you really know the recipient of your mail opted-in?
If you're sending mail to such addresses, you may be spamming.
It really doesn't matter how long you've had an address on-file, or where you got the address. Without confirmation, you may as well be sending to addresses you got from the latest "Millions CD."
As for CAN-SPAM, it's just a law that specifies certain types of spam and certain email practices are criminal violations of US law. It is not a definition of what is or is not spam.