131hub/postfix repository overview

⁠Motivation

131hub/postfix⁠ is a docker image bringing simple postfix container.

⁠How to run it

The following env variables need to be passed to the container:

• SMTP_SERVER Server address of the SMTP server to use.
• SMTP_PORT (Optional, Default value: 587) Port address of the SMTP server to use.
• SMTP_USERNAME (Optional) Username to authenticate with.
• SMTP_PASSWORD (Mandatory if SMTP_USERNAME is set) Password of the SMTP user. If SMTP_PASSWORD_FILE is set, not needed.
• SERVER_HOSTNAME Server hostname for the Postfix container. Emails will appear to come from the hostname's domain.

The following env variable(s) are optional.

• SMTP_HEADER_TAG This will add a header for tracking messages upstream. Helpful for spam filters. Will appear as "RelayTag: ${SMTP_HEADER_TAG}" in the email headers.

• SMTP_NETWORKS Setting this will allow you to add additional, comma seperated, subnets to use the relay. Used like -e SMTP_NETWORKS='xxx.xxx.xxx.xxx/xx,xxx.xxx.xxx.xxx/xx'

• SMTP_PASSWORD_FILE Setting this to a mounted file containing the password, to avoid passwords in env variables. Used like -e SMTP_PASSWORD_FILE=/secrets/smtp_password -v $(pwd)/secrets/:/secrets/

• ALWAYS_ADD_MISSING_HEADERS This is related to the always_add_missing_headers⁠ Postfix option (default: no). If set to yes, Postfix will always add missing headers among From:, To:, Date: or Message-ID:.

• OVERWRITE_FROM This will rewrite the from address overwriting it with the specified address for all email being relayed. Example settings: OVERWRITE_FROM=[email protected]⁠ OVERWRITE_FROM="Your Name" [email protected]⁠

⁠A note about using gmail as a relay

Gmail by default does not allow email clients that don't use OAUTH 2⁠ for authentication (like Thunderbird or Outlook). First you need to enable access to "Less secure apps" on your google settings⁠.

Also take into account that email From: header will contain the email address of the account being used to authenticate against the Gmail SMTP server(SMTP_USERNAME), the one on the email will be ignored by Gmail unless you add it as an alias⁠.

⁠Credits

• 131⁠;
• juanluisbaptiste/docker-postfix's inspiration⁠
• Alexandre Ellert tips