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'''`postfix(1)`''' is an [[Email/SMTP|SMTP]] [[Email/MTA|mail transfer agent]]. |
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| Most distributions include a `postfix` package. | Most [[Linux]] and [[BSD]] distributions offer a `postfix` package. |
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| The daemon (named `master`) is started by running: | For `systemd`-capable systems, [[Linux/Systemd|start and enable]] `postfix.service`. For BSD distributions, try: |
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| === Within a container === | === Containers === |
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| 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 [[Docker/Dockerfile#Run_in_foreground|defies]] the architecture of modern containers. | `postfix(1)` is designed to be launched from userspace, rather than being a binary that can be invoked in the foreground. However, a new `start-fg` subcommand was added in version 3.3. |
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| 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 [[Docker/Dockerfile#Use_a_supervisor|running a supervisor]]. Consider the following configuration for [[Supervisord]]: |
Consider the following [[Docker/Dockerfile|Dockerfile]] as a template. |
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| [supervisord] childlogdir=/var/log/supervisord logfile=/dev/stderr logfile_maxbytes=0 nodaemon=true user=root |
FROM alpine:latest RUN apk add --no-cache postfix EXPOSE 25 CMD ["postfix", "start-fg"] }}} |
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| [program:postfix] autostart=false command=postfix start startsecs=0 redirect_stderr=true |
To publish this service on an interface like 10.0.0.1, try: {{{ sudo docker build --tag postfix . sudo docker run --detach --name my-postfix \ --restart=always \ --publish 10.0.0.1:25:25 \ postfix |
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| Set `myhostname` and `mydomain` to the machines hostname. If the machine is acting as the mailserver for an entire domain, set `myorigin` to that name. === Split Routing === Sometimes mail needs to terminate at different services. Try: {{{ local_transport = local:$myhostname transport_maps = lmdb:/etc/postfix/transport }}} `/etc/postfix/transport` should look like: {{{ lists.myhostname.localdomain lmtp:unix:/tmp/lists.sr.ht-lmtp.sock myhostname.localdomain local:myhostname }}} Finally, run `postmap /etc/postfix/transport` and a hashed file will be produced. If your `postmap(1)` does not use LMDB, replace the `lmdb:` with whatever algorithm ''was'' used. === Address Rewriting === To masquerade as another email, try: {{{ smtp_generic_maps = lmdb:/etc/postfix/generic }}} `/etc/postfix/generic` should look like: {{{ @myhostname.localdomain [email protected] }}} Finally, run `postmap /etc/postfix/generic` and a hashed file will be produced. If your `postmap(1)` does not use LMDB, replace the `lmdb:` with whatever algorithm ''was'' used. === 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 }}} `/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. |
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=== 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 }}} Alternatively, try using [[Telnet|telnet]]. |
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| ---- == See also == [[https://man.archlinux.org/man/postfix.1|postfix(1)]] |
Postfix
postfix(1) is an SMTP mail transfer agent.
Contents
Installation
Most Linux and BSD distributions offer a postfix package.
For systemd-capable systems, start and enable postfix.service.
For BSD distributions, try:
postfix start
Containers
postfix(1) is designed to be launched from userspace, rather than being a binary that can be invoked in the foreground. However, a new start-fg subcommand was added in version 3.3.
Consider the following Dockerfile as a template.
FROM alpine:latest RUN apk add --no-cache postfix EXPOSE 25 CMD ["postfix", "start-fg"]
To publish this service on an interface like 10.0.0.1, try:
sudo docker build --tag postfix . sudo docker run --detach --name my-postfix \ --restart=always \ --publish 10.0.0.1:25:25 \ postfix
Configuration
Set myhostname and mydomain to the machines hostname. If the machine is acting as the mailserver for an entire domain, set myorigin to that name.
Split Routing
Sometimes mail needs to terminate at different services. Try:
local_transport = local:$myhostname transport_maps = lmdb:/etc/postfix/transport
/etc/postfix/transport should look like:
lists.myhostname.localdomain lmtp:unix:/tmp/lists.sr.ht-lmtp.sock myhostname.localdomain local:myhostname
Finally, run postmap /etc/postfix/transport and a hashed file will be produced. If your postmap(1) does not use LMDB, replace the lmdb: with whatever algorithm was used.
Address Rewriting
To masquerade as another email, try:
smtp_generic_maps = lmdb:/etc/postfix/generic
/etc/postfix/generic should look like:
@myhostname.localdomain [email protected]
Finally, run postmap /etc/postfix/generic and a hashed file will be produced. If your postmap(1) does not use LMDB, replace the lmdb: with whatever algorithm was used.
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
/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
Alternatively, try using telnet.
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