Postfix Docker Container

Postfix SMTP Relay.

Drop-in container for SMTP relaying. Use wherever a connected service requires SMTP sending capabilities. Supports TLS out of the box and DKIM (if enabled and configured).

Environment Variables

MAILNAME - set this to a legitimate FQDN hostname for this service (required).
MYNETWORKS - comma separated list of IP subnets that are allowed to relay. Default 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
LOGOUTPUT - Syslog log file location. eg /var/log/maillog. Default /dev/stdout.

General Postfix:

SIZELIMIT - Postfix message_size_limit. Default 15728640.
RELAYHOST - Postfix relayhost. Default empty.
POSTFIX_ADD_MISSING_HEADERS - add missing headers. Default no
INET_PROTOCOLS - IP protocols, eg ipv4 or ipv6. Default all
BOUNCE_ADDRESS - Email address to receive delivery failure notifications. Default is to log the delivery failure.
HEADER_CHECKS - If "true" activates a set of pre-configured header_checks.

TLS parameters:

USE_TLS - Enable opportunistic TLS. Default yes
TLS_KEY - Default /etc/ssl/private/ssl-cert-snakeoil.key
TLS_CRT - Default /etc/ssl/certs/ssl-cert-snakeoil.pem
TLS_CA - Default ''

NB. A "snake-oil" certificate will generated on start if required.

DKIM parameters:

USE_DKIM - Enable DKIM. Default no
DKIM_KEYFILE - DKIM Keyfile location. Default /etc/opendkim/dkim.key
DKIM_DOMAINS - Domains to sign. Defaults to MAILNAME. Multiple domains will use the same key and selector.
DKIM_SELECTOR - DKIM key selector. Default mail. <selector>._domainkey.<domain> is used for resolving the public key in DNS.
DKIM_INTERNALHOSTS - Defaults to MYNETWORKS.
DKIM_EXTERNALIGNORE - Defaults to MYNETWORKS.
DKIM_OVERSIGN_HEADERS - Sets OversignHeaders. Default From.
DKIM_SENDER_HEADERS - Sets SenderHeaders. Default unset.
DKIM_SIGN_HEADERS - Sets SignHeaders. Default unset.
DKIM_OMIT_HEADERS - Sets OmitHeaders. Default unset.

Usage Example

docker run -e MAILNAME=mail.example.com panubo/postfix

Volumes

No volumes are defined. If you want persistent spool storage then mount /var/spool/postfix outside of the container.

Test email

To send a test email via the command line, make sure heirloom-mailx is installed.

echo -e "To: Bob <bob@example.com>\nFrom: Bill <bill@example.com>\nSubject: Test email\n\nThis is a test email message" | mailx -v -S smtp=smtp://... -S from=bill@example.com -t

# With TLS
echo -e "To: Bob <bob@example.com>\nFrom: Bill <bill@example.com>\nSubject: Test email\n\nThis is a test email message" | mailx -v -S smtp-use-starttls -S ssl-verify=ignore -S smtp=smtp://... -S from=bill@example.com -t

# With TLS on Centos/Fedora (extra nss-config-dir)
echo -e "To: Bob <bob@example.com>\nFrom: Bill <bill@example.com>\nSubject: Test email\n\nThis is a test email message" | mailx -v -S smtp-use-starttls -S ssl-verify=ignore -S nss-config-dir=/etc/pki/nssdb -S smtp=smtp://... -S from=bill@example.com -t

Developing

See the Makefile for make targets. eg To build run make build.

Status

Production ready and stable.

jebw / docker-postfix