And additionally some simple “link” (that you also don’t have to click in the email but can easily type in yourself) to a corresponding info text on the Bitwarden website, like:
If you want to know more about this change, go to https://bitwarden.com/legacy-encryption/ (or whatever link it could be)
That info text then could be like the one that @Micah_Edelblut posted after our discussion: Deprecating support for legacy accounts
→ that way, everyone who received such a mail, could easily check the content and validity of that mail with an official info on the official Bitwarden website