Have you read my reply?
If I help you, or if you figure it out on yourself, your system becomes open to every spammer on the planet.
So I won't help you.
Which is a good thing.
Because if I did, I'd have to add you to all the blocklists and your mail wouldn't get anywhere.
Follow my suggestions for using either SMTP Authentication or POP before SMTP authentication on your client's machines. That's what the rest of us do.
I can't tell you how to do that because each email client is different. But it can be done, and must be done if your users are to use your email server for outgoing email.
Jeff