The whole appeal of email-style decentralization is that even in those cases, Google can only block you from GMail - not email as a whole, which would be far more deleterious, and is the ever-present threat in non-decentralized platforms.
1. https://www.litmus.com/email-client-market-share
2. https://www.oberlo.com/statistics/most-used-email-clients
People add their Gmail account to their iPhone and get Apple Mail.
Virtually all email goes to Gmail between personal accounts and GSuite stuff.
...and what a miserable bunch most of them were: 2 MB attachment limits and 10 MB mailbox quotas?! GMail had to drag all of them kicking and screaming into the 21st century when they debuted with a 1 GB mailbox quota.