This message was deleted.

A simple re-engagement email sequence always helps. I usually talk about how things have changed since we last spoke, mention a few product updates - relevant to the audience, of course (do this by segmenting the mailing list into categories/reasons for churn beforehand) - I also mention a few of the newer clients who've come into the picture, and wrap the email up by asking for a quick call to see if they would be interested in trying the product out again. Offering a discount also works, but I haven't tried those sequences myself so can't help you there. But yes, a simple reengagement email sequence, then retargeting ads based on the responses/actions on the emails, works great.

Thanks @Shoaib Ahmed!