We run a small postfix (and dovecot) mail server for a number of hosted domains, using virtual alias maps and with spamassassin configured.
Recently it's become apparent that we're generating some backscatter; spam emails are coming into non-existant email addresses and they are being bounced back to the forged sender. This is obviously a problem in terms of reputation for our mail server and also means we're spamming on behalf of the spammers.
What I want to do then is change the postfix behaviour so that, instead of generating a bounce email form MAILER-DAEMON the mail is rejected during the SMTP transaction.
I've tried adding local_recipient_maps (http://www.postfix.org/LOCAL_RECIPIENT_README.html), but this made no difference. I think this is because I'm using virtual_alias_maps (and other virtual mailbox solutions don't seem to apply here either).
postconf -n generates:
alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5 html_directory = no inet_interfaces = all inet_protocols = all local_recipient_maps = proxy:unix:passwd.byname $alias_maps mail_owner = postfix mail_spool_directory = /var/spool/mail mailbox_size_limit = 0 mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man message_size_limit = 0 mydestination = $myhostname, localhost.$mydomain, localhost mydomain = verrotech.com myhostname = mail.verrotech.com newaliases_path = /usr/bin/newaliases.postfix queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.10.1/README_FILES sample_directory = /usr/share/doc/postfix-2.10.1/samples sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination smtpd_sasl_auth_enable = yes smtpd_sasl_path = private/auth smtpd_sasl_type = dovecot smtpd_tls_auth_only = yes smtpd_tls_cert_file = /etc/letsencrypt/live/mail.domain.com/fullchain.pem smtpd_tls_key_file = /etc/letsencrypt/live/mail.domain.com/privkey.pem smtpd_tls_security_level = may unknown_local_recipient_reject_code = 550 virtual_alias_maps = hash:/etc/postfix/virtual