Postfix - Mail Solution for RPi

I recently wrote about setting up nullmailer as an ideal solution for mailing out of a Raspberry Pi. It turns out that nullmailer has some severe limitations. Not least of which is that it continues to try to send rejected emails. Forever. Every minute ( by default ).

That's not good. Perhaps there are some configuration tricks for nullmailer that get over this problem. I decided to take a look at how easy it was to setup Postfix as a null (send only) smtp service. It turned out it is relatively simple. Once set up it is very easy to reconfigure Postfix to handle your outgoing mail in any number of ways.

I wondered if first time mail configurers might have trouble getting to grips with what's needed. So I produced a commented script that will do it for you (below).

First, install Postfix and sasl.

sudo apt-get -y update

sudo apt-get -y install libsasl2-modules postfix

You will be asked for a hostname, the type of postfix server to setup and an smtp server during the postfix package install. It does not really matter what you enter as the script will overwrite the configuration anyway but you can accept the defaults for hostname and smtp server while selecting 'Satellite Server' as the type to install.

Alter the 8 configuration variables at the top of the script to suit your requirement and then run with:

sudo perl setuppostfix.txt

As always when running as root ( sudo ) make sure you have read the script and are happy with what it does,

Downloadable settuppostfix.txt here.

If you intend to use your GMail account as an outbound smtp server, you can set up an App Password for authentication.

The script is fully commented but a brief outline of what it does:

given:

• your hostname is raspberrypi
• your mailername is raspberrypi.local
• smtp server smtp.gmail.com on port 587,
• smtp login name yourname@gmail.com with password 'mypasswd',
• want to send root and pi mail to mymail@mydomain.com
• want to use a 'from/replyto' address of raspiadmin@mydomain.com

writes your mailername to /etc/mailname
raspberrypi.local

writes to /etc/aliases
postmaster:    root
root:          mymail@mydomain.com
pi:            mymail@mydomain.com

writes to /etc/postfix/generic
@raspberrypi            raspiadmin@mydomain.com
@raspberrypi.local      raspiadmin@mydomain.com
@localhost.localdomain  raspiadmin@mydomain.com
@localhost              raspiadmin@mydomain.com

writes to /etc/postfix/smtp_auth
[smtp.gmail.com]:587 yourname@gmail.com:mypasswd

writes to /etc/postfix/main.cf using the template at the end of the script.

I hope it proves useful. I'm certainly pleased with the 'upgrade' myself.

-------------------------------------------------------------
#!/usr/bin/perl
use strict;
use warnings;

#----------------------------------------
# THIS SCRIPT WILL OVERWRITE ANY EXISTING
# POSTFIX CONFIGURATION
#----------------------------------------

#----------------------------------------
# This script will perform a simple setup
# of the Postfix mail agent for use as
# a send-only mailer on the Raspberry Pi
# running Raspbian Wheezy/Squeeze/Buster.
# It has been tested as a setup for using
# a Google Mail account for sending email
# and using an ISP smart smtp relay.
# Read through the script to check what it
# does and then run using sudo as a user
# with sudo permissions.
#
# sudo perl setuppostfix.txt
#----------------------------------------

#----------------------------------------
# Configuration
# Alter the 8 items below to suit
# your required configuration. The items
# are described in the following sections
#----------------------------------------

my $fromuser      = 'yourname@gmail.com';
my $adminuser     = 'yourname@gmail.com';
my @adminmaps     = qw( root pi );
my $smtpserver    = 'smtp.gmail.com';
my $smtpport      = 587;
my $loginname     = 'yourname@gmail.com';
my $loginpassword = 'yourloginpassword';
my $mailname      = 'raspberrypi.local';

#----------------------------------------
# $fromuser
#----------------------------------------
# Provide an email address to be used for
# the from and reply-to addresses in emails
# FROM local users on this raspberry Pi.
# When you send mail through your ISP's or
# your own smart smtp relay, there must be
# a valid return address where smtp servers
# between you and the final destination can
# return messages. That ought to be your
# Raspberry Pi but as it is unlikely that
# you have your Pi set up as a visible
# internet server, you must provide an email
# address to be used as the From and
# Reply-To address when local users on your
# Raspberry Pi ( e.g. root@raspberrypi or
# pi@raspberrypi ) send email. The reply
# addresses will be rewritten so that the
# $fromuser email address is used instead.
# This only applies to mail that carries
# a 'local' From address. If your programs
# specifiy a real email address in sent mail
# that won't be rewritten.
# This re-writing is implemented by the
# Postfix  smtp_generic_maps facility.
# If you are using a Google Mail account
# to send your email, it doesn't really
# matter what you put in here. The Google
# servers will re-write whatever you put
# with your Google Mail address.
# If you are using your ISP smtp smarthost
# a genuine email address is probably
# mandatory. 

#----------------------------------------
# $adminuser and @adminmaps
#----------------------------------------
# If you wish, you may send mail destined
# for local users to an external email
# address. That is mail TO local users
# originating on this Raspberry Pi.
# The $adminuser variable contains
# the email address that you want to send
# these mails to. @adminmaps is a space
# separated list of local users whose mail
# you want to forward on.
# This is implemented using the /etc/aliases
# file. For the initial setup this is kept
# to a minimal simple implementation, but
# you can edit the file at any time to
# modify the settings and then run
# sudo newaliases
# to load them into Postfix

#----------------------------------------
# $smtpserver
#----------------------------------------
# This is the the remote smtp relay or
# mail account server. The server for
# Google Mail is already in the script
# so if you are using that you can leave
# it unchanged. Put your smart smtp relay
# in here if you are using one.

#----------------------------------------
# $smtpport
#----------------------------------------
# The port that your smtp server listens
# on. If you are using Google Mail then the
# correct port, 587, is already in the script
# so you can leave that.
# If you are using a smart smtp relay then that
# also most likely listens on port 587.
# You might be using an internal service that
# still listens on port 25, but if you are
# you'll most probably know about that anyway.
#------------------------------------------
# NOTE:
# starttls port 587 Vs wrapped ssl port 465
#------------------------------------------
# Postfix doesn't support 'wrapped ssl'
# communication directly. Servers that require
# this normally listen on Port 465. It is
# possible to use Postfix with wrapped ssl
# but it is beyond the scope of this simple
# script. Google for 'smtp 465 ssl Postfix'.
# Wrapped ssl is quite an old method of
# encrypting the smtp conversation so hopefully
# few people will come across this issue.

#------------------------------------------
# $loginname & $loginpassword
#------------------------------------------
# If you are communicating with a secure
# mail server on port 587 you'll need to
# provide login credentials. For your
# Google Mail account that will be your
# Google Email address and your Google
# login password, OR an app password you
# have created for GMail.
# This will be stored in
# /etc/postfix/smtp_auth and
# /etc/postfix/smtp_auth.db so it is
# essential that these files are readable
# only by root.

#----------------------------------------
# $mailname
#----------------------------------------
# The fully qualified domain name for your
# mail server. This will get written to
# /etc/mailname.

#------------------------------------------
# SCRIPT INNARDS START HERE - You don't
# need to edit anything from here on in
# but there's nothing to stop you if you
# wish.
#------------------------------------------

my $maincf   = '/etc/postfix/main.cf';
my $smtpauth = '/etc/postfix/smtp_auth';
my $generic  = '/etc/postfix/generic';
my $aliases  = '/etc/aliases';

my $servername = $smtpserver;
$servername =~ s/[\[\]]//g;
unless( $smtpport) {
    die 'You must provide an smtp port';
}
$servername = qq([$servername]:$smtpport);

#------------------------------------------
# Make sure we are running via sudo and
# have the necessary permissions.
#------------------------------------------

die 'run this script as root using sudo' if $<;
#------------------------------------------
# Fix mailname and hostname 
#------------------------------------------
my $mailhostname = qx(hostname);
chomp($mailhostname);
$mailhostname =~ s/[\s\r\n]//g;

system(qq(echo "$mailname" > /etc/mailname)) 
	and die 'failed to write /etc/mailname';

#------------------------------------------
# write the main /etc/postfix/main.cf file
#------------------------------------------

my $maincftemplate;

{
    my $protocols = 'ipv4';
    my $networks = '127.0.0.0/8';
    
    # check for ipv6
    my $procmods = qx(cat /proc/modules);
    die qq(failed reading /proc/modules : $?) if $?;
    if($procmods =~ /ipv6/) {
        $protocols .= ', ipv6';
        $networks .= ' [::ffff:127.0.0.0]/104 [::1]/128';
    }
    
    $maincftemplate = main_cf_template();

    $maincftemplate =~ s/REPLACEMAILNAME/$mailname/g;
    $maincftemplate =~ s/REPLACEHOSTNAME/$mailhostname/g
    $maincftemplate =~ s/REPLACESERVERNAME/$servername/g;
    $maincftemplate =~ s/REPLACEPROTOCOLS/$protocols/g;
    $maincftemplate =~ s/REPLACENETWORKS/$networks/g;
    
    open my $fh, '>', $maincf
        or die qq(failed to open $maincf : $!);
    print $fh $maincftemplate;
    close( $fh );
    chmod( 0644, $maincf );
}

#-----------------------------------------
# Write the generics file
#-----------------------------------------
if($fromuser){
    open my $fh, '>', $generic
        or die qq(failed to open $generic : $!);
        
    my($host, @discards) = split(/\./, $mailname);
    
    print $fh qq(\@$mailname    $fromuser\n);
    if($host ne $mailname) {
        print $fh qq(\@$host    $fromuser\n);
    }
    print $fh qq(\@localhost.localdomain    $fromuser\n);
    print $fh qq(\@localhost    $fromuser\n);
    close($fh);
    system(qq(postmap $generic))
       and die qq(failed to map generics : $!);
}

#-----------------------------------------
# Write the smtpauth
#-----------------------------------------
if($loginname && $loginpassword) {
    open my $fh, '>', $smtpauth
        or die qq(failed to open $smtpauth : $!);
    
    print $fh qq($servername $loginname:$loginpassword\n);
    close($fh);
    chmod(0600, $smtpauth) or
        die qq(failed to set permissions on $smtpauth : $!);
    
    system(qq(postmap $smtpauth))
       and die qq(failed to map generics : $!);
}

#-----------------------------------------
# Write the aliases
#-----------------------------------------

if( $adminuser && @adminmaps ){
    open my $fh, '>', $aliases
        or die qq(failed to open $aliases : $!);
        
    # add default post address
    print $fh qq(postmaster:    root\n);
    # add maps
    for( @adminmaps ) {
        print $fh qq($_:    $adminuser\n);
    }
    close($fh);
    system('newaliases')
        and die qq(failed calling newaliases : $!);
}

#------------------------------------------
# Restart Postfix and end
#------------------------------------------

system('/etc/init.d/postfix reload')
    and die qq(problems reloading Postfix : $!);
    
    
#------------------------------------------
# Send an email
#------------------------------------------

my $emailtext =
qq(From: root
To: root
Subject: Raspberry Mail Configuration
Content-type: text/plain

Your Raspberry Postfix is configured on $mailname
with the following configuration:

/etc/postfix/main.cf <<
$maincftemplate
);

{
    open my $fh, '|/usr/sbin/sendmail -t'
        or die 'could not open pipe to sendmail';
    print $fh $emailtext;
    close($fh);
}

print qq(Postfix configuration complete\n);

#-----------------------------------------
# Templates
#-----------------------------------------

sub main_cf_template {
    my $template = <<'MAINCFTEMPLATE'
# Basic Null ( send only ) Postfix

smtpd_banner = Raspberry Pi Mail
biff = no
append_dot_mydomain = no
readme_directory = no
myhostname = REPLACEMAILNAME
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = REPLACEHOSTNAME, REPLACEMAILNAME, localhost.localdomain, localhost

relayhost = REPLACESERVERNAME
inet_protocols = REPLACEPROTOCOLS

mynetworks = REPLACENETWORKS
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only
smtp_generic_maps = hash:/etc/postfix/generic

# TLS

smtp_use_tls=yes
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/smtp_auth
tls_random_source=dev:/dev/urandom
smtp_sasl_security_options=noanonymous
smtp_tls_security_level=may

MAINCFTEMPLATE
;
    return $template;
}

1;