I believe its possible to solve the vast majority of the problems that metamta.one-mail-per-recipient=false has and possibly remove some options including possibly metamta.recipients.show-hints metamta.public-replies and metamta.public-replies.
Best Of Both Worlds Config:
Create one email per user:
- Set the reply-to header to a secure per-user value. This overrides both "reply" and "reply all"
- Set the TO and CC header to the complete set of users
- (optional) Don't show TO and CC hints as the they are now in the header field
- mail to Mailing List users should generate reply-to with a hint to the user that no action was taken.
If you construct a different email per recipient, but include the complete header information you will get the following pros and cons:
Policy controls work correctly and are enforced per-user.
Recipients can see To/Cc at a glance.
If you use mailing lists, you won't get duplicate mail if you're a normal recipient and also Cc'd on a mailing list.
"Reply All" no longer spams all other users.
both public and private reply-to addresses work.
Mails are sent in the language of user preference.
Getting threading to work properly is harder, and probably requires making mail less useful by turning off options.
This is actually questionable. This makes threading work better for me on some clients.