Hello there.

This is a very simple idea which could improve characters lifespan and, as well, increase retention rate (and, I am positive, significantly). So, how it works work:

1. Character types his email, like 'email example@gmail.com";
2. He starts to receive ingame notes to all, to himself, and if he is in a cabal - notes to cabal;
3. He receives notes of coming-soon eq purge (just a thought, not necessary, maybe even not a good idea);
4. He receives autodeletion warnings (important, imho);
5. When character deletes, email is purged from the mailing list.

Perhaps there could be others types of emails. From the coding aspect, it's easy to implement (and you already have a mail server with regular emails sending so it's only backend+smtp integration, which should be simple).

I would expect at least 70% open rate, with retention increased up to 30%. Subjective, of course.

Cheers!