How to stop unauthenticated user to send mail to my mailserver
port 25 and port 587 both are open at my mail-server... using port 587 user must need user-name:password for sending mail..... but using port 25 no user-name:password need to send mail to my mail-server users.... any non-exist user can also send mail to my users by using port 25 without authenticate. also my mail-server is not an open-relay.
So how can i stop sending mail from my mail-server( from email client like outlook etc) to my local users or any external emails for unauthenticated users. Simply i want that only authenticated users can send mail to my users.