Using Postfix for Secure SMTP Gateways

Improve your site's e-mail hygiene and make life difficult for spammers and hackers.

That's more than enough information to get you started. May your mail arrive promptly and the spamming filth stay out!


Mick Bauer is security practice lead at the Minneapolis bureau of ENRGI, a network engineering and consulting firm. He's been a Linux devotee since 1995 and an OpenBSD zealot since 1997, taking particular pleasure in getting these cutting-edge operating systems to run on obsolete junk. Mick welcomes questions, comments, and greetings sent to

Brenno de Winter, 28, is the Linux-focused president of De Winter Information Solutions. He started programming at the age of nine. In his daily routine he is involved in UNIX/Linux, databases, security, telephony-over-IP presentations, consulting and training. He's active in the Polder Linux User Group, has contributed to several GPL projects, including GnuPG, MySQL and TWIG, and is in the process of creating a brand-new project himself as well.



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how to local smtp

Anonymous's picture

Hello and thank you for the guide.

I changed inet_interfaces = localhost but it didnt worked.
I can receive but i can not send eimail
I quote the cf in order to have a look.

# See /usr/share/postfix/ for a commented, more complete version

# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# TLS parameters
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

myhostname = localhost
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = $myhostname, localhost.$mydomain, $mydomain
relayhost =
mynetworks = [::ffff:]/104 [::1]/128,

mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = localhost
default_transport = error
relay_transport = error
inet_protocols = ipv4

Did i missed something?

Sending from localhost only

Robsteranium's picture

Apparently setting the following in will ensure that only localhost can send emails:

inet_interfaces = localhost