Is it possible to secure postfix in a way, that incoming emails are checked on whether the email comes really from the sender?

Is that possible to write php script and chose a sender, like the mail is really coming from the sender and what are the possibilities for postfix to find out that this mail is not actually coming from the real sender?

What I have found out and activated are the options

smtpd_sender_restrictions = reject_unknown_sender_domain
unknown_address_reject_code = 554
smtpd_client_restrictions = reject_unknown_client
unknown_client_reject_code = 554

Please mention, whether I have missed out on any points!