FryeMail.me is the custom domain behind my personal email. Because I own the domain, my address stays the same no matter which service hosts my mail. I choose where my data lives, and moving to a new provider only takes a DNS update.
For sensitive correspondence, use whichever of these options fits what you already have set up.
Option 1
Download my public PGP key,
encrypt your message, and send it to [username]@s.fryemail.me.
The s. subdomain routes to a dedicated secure mailbox.
Option 2
Bitwarden Send allows end-to-end encrypted, time-limited message sharing with no account required on your end.