What is a re-engagement campaign?

Two or three messages over two weeks is the usual shape. Be direct about what is happening, make staying a single click, and say when the removal will take effect.

Response rates are low by design, commonly 1 to 5%. That is not a failure, because the campaign exists to separate the remaining few from the rest rather than to win everyone back.

Batch it and watch the numbers between batches. If complaints climb in the first thousand, stop and suppress the segment rather than sending the other forty thousand.

Honor the outcome. A sequence that ends with everyone still on the list is a formality, and the addresses you were about to remove are the ones most likely to have become traps.

Say 40,000 people on your list haven't clicked anything in nine months. You verify the segment first and 5,200 come back invalid, so you suppress those and work with 34,800.

You send 2,000 a day. Message one goes out with the subject Still want these emails? and a single button that says Keep me subscribed. Five days later, non-responders get We're about to stop emailing you. A week after that comes a last short note giving the date.

Across the whole run, 1,040 people click to stay, which is 3% and quite normal. Complaints on the first two batches come in at 0.08%, so you keep going. The other 33,760 are suppressed on the date you promised. Your active list gains 1,040 proven readers, and nearly 39,000 addresses stop counting against you at every mailbox provider.

Opens can't be your test, because Apple's Mail Privacy Protection fetches images for many messages whether or not the person ever looks at them. An open from an Apple Mail user proves nothing. Count a click on the stay button, a reply, a purchase or a login.

Clicks have their own false positives, since corporate security scanners follow links in incoming mail to check them for malware, which registers as a click. The signature is easy to spot once you look: every link in the message clicked within a few seconds of delivery, often from a data center IP. Discount those, or a chunk of your most dormant corporate addresses will appear to have enthusiastically re-subscribed.

Think about what you're asking, too. A discount code gets clicks from people who want the discount and still won't read your mail. If the goal is a list of people who want to hear from you, the plain question works better than a bribe, even though it gets a lower response.