Use a re-engagement campaign to get inactive subscribers back on board.

Cleaning your email list allows you to actually reach your recipients, but don't delete subscribers without checking in first. Use a re-engagement campaign to bring your them back into the fold.

Re-engaging subscribers is four to eight times cheaper than finding new ones. So while it's a good idea to remove inactive subscribers from your email list, it's not a good idea to give them the boot without trying to re-engage them first. The best time to begin a re-engagement campaign varies, but 90 days without opening an email is generally a good starting point. Win them back with an offer or by making your value clear (with social proof, "best of" lists, etc.). Obviously, if people aren't opening your emails, you'll need to convey much of this in your subject lines. For recipients who aren't swayed, gradually decrease the number of emails you're sending and see if they start reading again. Finally, if that doesn't work, let them go. Send a goodbye email that either informs them that they've been unsubscribed (giving them the option to opt back in) or tells them that they will be unsubscribed in X days. For the customers who do re-engage, make sure to put them into a new segment in your list, as they are high-risk. And very importantly, make sure this whole process happens quickly and painlessly.