Hey, if you're running a marketing program, if you manage a marketing list, I have to ask: Are you tracking where and when and how each recipient signs up for your email list?
Surprisingly, I'm finding that many marketing managers aren't tracking this. This is sad, because sometimes this data is the last line of defense against you getting sanctioned over allegations of sending spam.
When an ISP, ESP, or recipient asks for proof that a recipient opted-in to your email, they're asking for those exact details. It's typically enough proof to demonstrate that the person who is now complaining really did sign up for your email messages. It's important data to help defuse "he said, she said" situations where a spam complainant alleges that a sender is harvesting addresses.
Sometimes people try to fake this data; and it's not always perfect. But that's not the point I'm trying to make. My point is that there seem to be a lot of list managers who don't even bother to track it at all.
Sometimes a high tech solution isn't even necessary. Are you managing a small list of only friends and relatives, all of whom have verbally opted-in? Write it all down in an Excel spreadsheet, so that years from now, when and if somebody complains, you don't have to rack your brain trying to remember who Bobby is related to and when he asked you to be on that list.
Are the people on your list buyers of your product, who opted-in during a purchase? Keep transaction records that detail that information. Date, time, home address, IP address from which they placed the order, what product they bought, how much they paid. If a blacklist takes issue with your mail to one of those recipients later, this data (and information about how your purchase process works) is going to be very helpful to demonstrate that this person really did sign up.
Is your list process a lead nurturing kind of thing, where your salespeople are verbally asking people if it's OK to sign them up for a list? Don't rely on your salespeople alone to track this; use your ESP's web signup and double opt-in functionality to help protect you. When a salesperson hears a "yes" response, have them fill out the web signup form, generating an opt-in request to the recipient. The recipient clicks, the ESP tracks it, the person is opted-in, and your ESP now has darn near infallible proof of opt-in.
I used to run the mailing list for a friend's music venue, and we did something very similar. Paper signup form in the venue, which we took and used to fill out the signup form, generating the double opt-in request. It worked very smoothly.
Don't assume that offering to unsubscribe the complainer will resolve a spam complaint issue. Any time you're dealing with a savvy ISP, ESP, or anti-spam group, they're invariably asking for proof off opt-in, and they're likely to terminate, block, or blacklist you. "I have unsubscribed the complainer," is a great answer, but to the wrong question - "Did you unsubscribe them?" was NOT the question being asked.
If you manage a list, and you don't track how each recipient signed up, eventually you're going to run in trouble. Maybe not today, maybe not tomorrow. Maybe you'll get away with it for two years. But eventually you'll end up blocked or blacklist, forced to stop mailing or forced to reconfirm your list (effectively "throwing out" most of it), and wouldn't it be better to protect yourself against an issue like that now, today, before it becomes an issue?