How would the user “TAG” the e-mail?
It would be a manual process I assume.
Why not have them just move it to the shared folder?
This would work for the message one time but as for future related messages
that’s different. If they do not do a “reply” to a continuing message or change the e-mail subject line I do not see this being done.
They may also just send a new message with a different subject line and this would bypass sending it to your shared public folder.
I’d be curious if anyone has a sloution.