At work, I'm facing security risk with the mail sender spoofing. I have a relay mail server which accepts mail relay from all server subnets.
If an user in a normal server sends mail within command line:
user@server$ echo mail_content | mail -r firstname.lastname@example.org -s Important email@example.com
So basically, this guy can pretent to be anyone when sending email, which could lead to really big trouble
What I'm expecting is, even though running the above command, the recipient still get the mail with
How can I do it in Postfix?
Edit: I forgot to add, the authentication method is Active Directory, not sure if it makes the configuration much complicated :)