Flag email when composing

any way to put a yellow flag when sending the email?

I want a green flag when sending emails to fellow members of the Green Party. Particularly troublesome when replying to messages that are flagged. All other messages should not have a flag at all.

I have wondered about defining (Apple Mail) rules to add the green flag when any of my fellow Greens are listed as recipients. This would match the rule I have for incoming messages from the same people.

in my case i want to put a yellow flag in the emails im waiting for a reply.

i have to do it manually, first send all emails, then go to the sent items and flag the mails im waiting…

it would be great to put the flag when sending the email