@JustinDerrick @reay I wrote a privacy guide about emails when working for IVPN
https://www.ivpn.net/privacy-guides/email-and-privacy/
Basically, you should avoid emails if you care about privacy, there is nothing private about emails. Your email provider can read your sent/received emails and each recipient provider can do the same.
ProtonMail, Tuta, Posteo, Mailbox.org and custom encryption at rest will not fix the statement above. The encryption at rest done only prevent them from reading currently stored emails.
End-to-end encryption can help but they still know who send emails to who, at which frequency and each email size.