I've not seen many campaigns like this, so thought it'd be a good share.

This email from software house Realmac is almost entirely about unsubscribing - giving people who aren't interested in receiving future emails a chance to opt out, and in the process tidying up their list.

I'm not sure if they did any data behind this, but this is the kind of thing that could be sent to an unengaged segment, as part of a larger strategy.