My title pretty much sums it up I have recently setup a sendonly postfix server i used this guide https://www.linuxbabe.com/mail-server/postfix-send-only-multiple-domains-ubuntu#generate-dkim-keypair It works as expected.
The purpose of this server is to be used by our hosted websites to send the website mail. My server sends successfully from the three test domains i have used
I would like to lock down the ability to send from any particular domain with smtp auth
So a username and password for each domain i have setup.
Is this possible? any guidance is appreciated