Out of scope isn't about how hard to implement is a given feature. Is about stuff that doesn't need to be added to Chevereto.
You are asking for an email marketing tool, no way I will add that. There are countless services and scripts for that because is not just a weekend job and at this time I think that is wiser to work in features more related to image hosting which is what Chevereto does.
If you want to get the emails from your users you can simple run:
Code:
SELECT user_email chv_users WHERE user_newsletter = 1;
From there you can send your email using any email marketing tool.