postfix - send from any user?

[salam]

on a system, where more users have mail accounts - any user (no need of root access) can send a mail which looks like it was send by other user.

telnet localhost 25
...
...
mail from: anything@domain.tld
...
...
...

can this somehow be prevented without iptables blocking?

[indynet]

Sure, by default postfix relay email from localhost. You should setup SMTP autentication by SASL for example.

Look at manual for smtpd_recipient_restrictions and SASL[/code]