Originally Posted by admins
May how could I deactivate port 25 for outgoing mails?
That doesn't sound like a very good idea? The server even if you are only receiving emails still has to send out bounce messages and other communication.
This line in the master.cf file pretty much explains what you need to do to secure the server from spammers.
#submission inet n - - - - smtpd
# -o smtpd_enforce_tls=yes
# -o smtpd_sasl_auth_enable=yes
# -o smtpd_client_restrictions=permit_sasl_authenticated,reject
Of course you want to remove any #'s in there.
This is all explained in various How To's on the site. A little searching will pull this information up with out a problem.