Long time FastMail user. Never got a straight answer on privacy so moved to Tutanota for now. Much better, end to end encryption- nice clients too.
FastMail seems to have automated default address collection, backup of drafts & deleted email, ability to archive email. With no at rest encryption this could be possibly used for data mining too.
This new law is the last straw. So far they have not bothered to address the issue. Till few years back FM used to be awesome but feel they have not moved with time.