CBSubs Mailer must be able to email also to users that have been blocked, e.g. by a CBSubs plan.

If that is unwanted, you can just edit the settings of the mailer in Group tab, Buyer usergroup conditions,
Applicable for View Access Level and change it from Public to Registered if your View Access levels correspond to that normal situation, otherwise you can select joomla user groups specifically below that setting.

EDIT: That will not fix the blocked user issue! We need a separate setting for this! Added a FR to implement this:

forge.joomlapolis.com/issues/7954

Ok, latest, just released, nightly build has a new setting for CBSubs Mailers forge.joomlapolis.com/issues/7954 (and also for CBSubs Promotions forge.joomlapolis.com/issues/7955 ) to make the Mailer applicable only to enabled users (or only for blocked users) or for all users (like is the case now, and that is the default value for backwards compatibilty, and because it may have unexpected results for users that are just registered but not yet confirmed, or just expired users where there is no login without a valid subscription).

The new settings of the mailer (and promotions too) is in Group tab, Buyer usergroup conditions, just above the existing "Applicable for View Access Level".