Postfix

Installation

Most distributions include a postfix package.

The daemon (named master) is started by running:

postfix start

On some systems, you should instead start and enable the postfix.service service.

Within a container

The bad news is that the Postfix service is designed to be launched from userspace using postfix(1), rather than being a binary that can be invoked in the foreground. This defies the architecture of modern containers.

The good news is that running Postfix in a standalone container is barely useful. Postfix will likely need to run alongside at least one other service. The solution to both issues is running a supervisor.

Consider the following configuration for Supervisord:

[supervisord]
childlogdir=/var/log/supervisord
logfile=/dev/stderr
logfile_maxbytes=0
nodaemon=true
user=root

[program:postfix]
autostart=false
command=postfix start
startsecs=0
redirect_stderr=true

Configuration

Relay mail

To relay mail through another SMTP server, such as GMail, try:

relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_security_options = noanonymous
smtp_sasl_password_maps = lmdb:/etc/postfix/sasl/sasl_passwd
smtp_tls_security_level = encrypt
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

And /etc/postfix/sasl/sasl_passwd should look like:

[smtp.gmail.com]:587 [email protected]:notarealpassword

Finally, run postmap /etc/postfix/sasl/sasl_passwd and a hashed file will be produced. If your postmap(1) does not use LMDB, replace the lmdb: with whatever algorithm was used.

Administration

Testing the service

Install mailx and send an empty email.

To test mail relay to external hosts, try:

mail -s 'Test Email' '[email protected]' </dev/null

Reviewing the queue

Two useful administrative utilities exist for reviewing the mail queue: postqueue(1) and postcat(1).

To view the mail queue, try:

postqueue -p

This will display the queued messages, the senders and recipients, and a mail ID.

To force all queued mail to be sent now, run:

postqueue -f

To instead force a singular message to be send now, run:

postqueue -i MAILID

To instead inspect a message in the queue, try:

postcat -vq MAILID

CategoryRicottone