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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. The daemon (named `master`) is started by running: |
Most [[Linux]] and [[BSD]] distributions offer a `postfix` package. For `systemd`-capable systems, [[Linux/Systemd|start and enable]] `postfix.service`. For BSD distributions, try: |
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| === 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 [[Docker/Dockerfile#Run_in_foreground|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 [[Docker/Dockerfile#Use_a_supervisor|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 }}} |
=== 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 [[Docker/Dockerfile|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 }}} ---- == Usage == For unencrypted and unauthenticated connections, try a connection string like `smtp+insecure+none://example.com:25`. When running a server that listens on port 465, with |
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| Before trying to configure Postfix, ensure that you understand the [[Postfix/Design|design]] of Postfix. See also [[Postfix/Encryption|encryption]] and [[Postfix/Authentication|authentication]]. === Receiving Mail === Set `myhostname` and `mydomain` to the fully-qualified names. Set `mydomains` to the set of all 'trusted' networks. Set `mydestination` to the set of all domains that should be considered 'local'. {{{ myhostname = www1.example.com mydomain = example.com mynetworks = 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 mydestination = $myhostname $mydomain www.$mydomain localhost localhost.localdomain }}} By default mail is only accepted... * from clients in trusted networks (`$mynetworks`) * from clients that authenticated with SASL * for remote addresses matching `$relay_domains` * for local addresses found in `$mydestination` (defaulting to `$myhostname`, `localhost.$mydomain`, and `localhost`) To adjust restrictions, try configuring `smtpd_relay_restrictions` or (the older and less-preferred method) `smtpd_recipient_restrictions`. === Routing Mail === To route mail based on the recipient domain, try: {{{ transport_maps = lmdb:/etc/postfix/transport }}} A `transport(5)` file (i.e. `/etc/postfix/transport`) looks like: {{{ admin@localhost relay:[smtp.gmail.com]:587 service1.example.com lmtp:unix:/path/to/service.sock example.com lmtp:0.0.0.0:24 .example.com lmtp:0.0.0.0:24 localhost local .localdomain local * relay:[smtp.gmail.com]:587 }}} The first part of each line is a pattern. The second part is an instruction: * a `local` instruction attempts [[Postfix/LocalDelivery|local delivery]] to the specified address * a bare `local` instruction expands to the `local_transport` setting, which itself defaults to `local:$myhostname` * a `lmtp` instruction forwards mail to an [[Email/LMTP|LMTP]] server * a `smtp` instruction forwards mail to an [[Email/SMTP|SMTP]] server * a `relay` instruction causes mail to [[Postfix/Relaying|relayed]] Bracketing an address prevents a [[Protocols/DNS#Records|MX record]] lookup; the [[Protocols/DNS#Records|A record]] alone is looked up and used naively. If even A record lookup should be skipped (i.e. for a name defined in the [[Linux/Hosts|hosts file]]), additionally specify `smtp_dns_support_level = disabled`. Domains prefixed with a dot (`.`) are a pattern for all subdomains. The example above captures `localhost` and `*.localdomain` for local delivery. The asterisk (`*`) domain is a fallback route, used only if nothing else matches. The matching happens in the hierarchical order shown above: by full address, then by full domain part, then by subdomain part, and finally the fallback. 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 === See [[Postfix/Rewriting|here]]. === Posting Mail === `master(8)` expects mail posted locally to use `$myhostname` as the sender's domain. To override this, set `myorigin`. {{{ myorigin = $mydomain }}} |
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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)]] [[https://www.postfix.org/documentation.html|Postfix project documentation]] |
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
Usage
For unencrypted and unauthenticated connections, try a connection string like smtp+insecure+none://example.com:25.
When running a server that listens on port 465, with
Configuration
Before trying to configure Postfix, ensure that you understand the design of Postfix.
See also encryption and authentication.
Receiving Mail
Set myhostname and mydomain to the fully-qualified names. Set mydomains to the set of all 'trusted' networks. Set mydestination to the set of all domains that should be considered 'local'.
myhostname = www1.example.com mydomain = example.com mynetworks = 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 mydestination = $myhostname $mydomain www.$mydomain localhost localhost.localdomain
By default mail is only accepted...
from clients in trusted networks ($mynetworks)
- from clients that authenticated with SASL
for remote addresses matching $relay_domains
for local addresses found in $mydestination (defaulting to $myhostname, localhost.$mydomain, and localhost)
To adjust restrictions, try configuring smtpd_relay_restrictions or (the older and less-preferred method) smtpd_recipient_restrictions.
Routing Mail
To route mail based on the recipient domain, try:
transport_maps = lmdb:/etc/postfix/transport
A transport(5) file (i.e. /etc/postfix/transport) looks like:
admin@localhost relay:[smtp.gmail.com]:587 service1.example.com lmtp:unix:/path/to/service.sock example.com lmtp:0.0.0.0:24 .example.com lmtp:0.0.0.0:24 localhost local .localdomain local * relay:[smtp.gmail.com]:587
The first part of each line is a pattern. The second part is an instruction:
a local instruction attempts local delivery to the specified address
a bare local instruction expands to the local_transport setting, which itself defaults to local:$myhostname
a lmtp instruction forwards mail to an LMTP server
a smtp instruction forwards mail to an SMTP server
a relay instruction causes mail to relayed
Bracketing an address prevents a MX record lookup; the A record alone is looked up and used naively. If even A record lookup should be skipped (i.e. for a name defined in the hosts file), additionally specify smtp_dns_support_level = disabled.
Domains prefixed with a dot (.) are a pattern for all subdomains. The example above captures localhost and *.localdomain for local delivery.
The asterisk (*) domain is a fallback route, used only if nothing else matches.
The matching happens in the hierarchical order shown above: by full address, then by full domain part, then by subdomain part, and finally the fallback.
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
See here.
Posting Mail
master(8) expects mail posted locally to use $myhostname as the sender's domain. To override this, set myorigin.
myorigin = $mydomain
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