3 elements of a good email permission reminder:
It’s specific.
Your permission reminder should be very thorough in explaining exactly how your recipient got on your email list. This is not the time to be terse. At the same time, you don’t want to list all possible ways someone might’ve been added. For example, if your permission reminder says, "You received this email because you purchased something from our stores, signed up online, dropped a business card in a fish bowl at a tradeshow, or signed up with a distributor/partner/affiliate sometime in the past" then it’s obvious that you’re a lazy jerk who just exported all your different databases, combined them into one list, and "blasted" an email out. Don’t be a lazy jerk. Setup different lists, and send very different welcome emails to them, each with different permission reminders.
Instead of writing, "You’re receiving this email because you’re a customer" try something more like, "You’re receiving this email because you’re a customer who opted-in for emails when you purchased something from our online store." Or, "You’re receiving this email because you signed up for email specials while making a purchase at one of our stores."
It’s polite.
Your permission reminder should be written in a way that shows you genuinely care about your recipients’ privacy, and you know that emailing them is a privilege, not a right. Don’t get me wrong. Your permission reminders don’t need to be full of apologies. Groveling is pathetic, and a waste of time. Just show some genuine concern. Sometimes, "concern" just means "details."
I’ve seen permission reminders written like, "This is not spam, as defined by U.S. Legislation ID Code 23298.2342.L32 Docket #ABC123." You know who quotes spam laws? Spammers.
I’ve seen permission reminders like, "This is just a one-time promotion, so there’s no need to report us for spamming." Just because it’s one time doesn’t mean it’s not spam. It just means I only have to report you for spamming one time. Jerk.
I’ve seen permission reminders like: "You’re receiving this email from Acme Widgets. If you don’t want them anymore, unsubscribe." Okay, but I already know I got this email from Acme Widgets, because you said it in the from: line, and your hideous logo is ginormous. The question is, "How the *&%$ did Acme Widgets get my email address?"
Show people that you took the time to write the permission reminder. Because they’re taking the time to read your permission reminder.
It’s provable.
This is where the "evidence" part comes into play the most. A good permission reminder will include some sort of indisputable proof that the recipient actually gave you permission to email them.
For example, "You are receiving our newsletter because you opted-in for it when you downloaded one of our whitepapers on software engineering."
With this kind of permission reminder, someone (such as an abuse desk admin at an ISP) can ask the complainer, "The permission reminder says you opted in when you downloaded their whitepaper. Well, did you opt-in, or not?"
Sure, people can lie and say they never heard of you. But any time I’ve ever investigated an abuse report, and had a permission reminder like this, the complainer is usually very honest. I get responses like, "Yes, I signed up for their newsletter, but good grief, they keep sending me the same friggin’ email offers over and over. I just want them to stop."
In that case, I don’t have to shut down the sender’s account. I can just tell them to stop being sloppy, and try to send more relevant, updated content.
I’ve also received responses from complainers, like, "Yes, the last guy who had this job downloaded that whitepaper, and signed up for those emails, but that idiot used the sales@ email address here, so now I’m getting these emails. Every time I try to call the sender, nobody answers. I just want the emails to stop." In that case, I can advise the complainer to click the unsubscribe link (or I do it for them).
If possible, you can merge customer information into your permission reminders.
For example, for some of our own Mailchimp system alerts, we tell people, "You are receiving this email because you are a registered customer of Mailchimp. Your username is ____ and your last login was on ____. "
I still get complaints from people, but at least they know why they got the email. They’ll write and say things like, "I don’t use Mailchimp anymore. Please delete my account."
Here’s an example of a permission reminder that lacks trackability (I’ve seen this one a lot): "You have received this email because you expressed interest in our product in the past." Okay, when? How? With whom did I express interest? All this means to me is that you purchased my email address from some affiliate who did the dirty list-aggregation work for you.
Better would be, "You have received this email because you requested more product information from Acme Widgets when you registered your ABC Widget." Ok, I don’t remember signing up for emails, but I do remember buying an ABC Widget, and I do remember filling out lots of forms for rebates and warranty registration. I’ll give them the benefit of the doubt and just unsubscribe, instead of reporting Acme Widgets for spamming me.
Note: In the above example, it would require Acme Widgets to actually segment their customer lists. Sure, it’s a little extra work, and it would be so much easier to blast out a big campaign to "everyone" instead. But remember #2 above? Showing genuine concern for the recipient? Who’s more important here? What’s a few more clicks in your email marketing system?
The point is, you want to write your permission reminder so that if/when it is turned into evidence, it can boil a dispute down to a simple yes-or-no scenario. Either you have opt-in proof, or not. Done. You don’t necessarily have to merge in the proof, but you should at least imply that you have the proof, if needed. If you can’t do that, the only implication for any judge is that you’re probably sending spam.
Re-cap
So let’s go back to that bad permission reminder, and review why it’s so bad.