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Consistency pass, formatting cleanup and fixes, introduce admonitions, add front-matter. --- docs: Add front-matter --- docs: Fix and format links - Some links were invalid (eg files moved or renamed) - Some were valid but had invalid section headers (content removed or migrated) - Some use `http://` instead of `https://` when the website supports a secure connection. - Some already used the `[name][reference]` convention but often with a number that wasn't as useful for maintenance. - All referenced docs needed URLs replaced. Opted for the `[name][reference]` approach to group them all clearly at the bottom of the doc, especially with the relative URLs and in some cases many duplicate entries. - All `tomav` references from the original repo prior to switch to an organization have been corrected. - Minor cosmetic changes to the `name` part of the URL, such as for referencing issues to be consistent. - Some small changes to text body, usually due to duplicate URL reference that was unnecessary (open relay, youtous) - Switched other links to use the `[name][reference]` format when there was a large group of URLs such as wikipedia or kubernetes. Github repos that reference projects related to `docker-mailserver` also got placed here so they're noticed better by maintainers. This also helped quite a bit with `mermaid` external links that are very long. - There was a Github Wiki supported syntax in use `[[name | link]]` for `fetchmail` page that isn't compatible by default with MkDocs (needs a plugin), converted to `[name][reference]` instead since it's a relative link. --- docs: Update commit link for LDAP override script Logic moved to another file, keeping the permalink commit reference so it's unaffected by any changes in the file referenced in future. --- docs: Heading corrections Consistency pass. Helps with the Table of Contents (top-right UI) aka Document Outline. docs: codefence cleanup --- docs: misc cleanup --- docs: Add Admonitions Switches `<details>` usage for collapsible admonitions (`???`) while other text content is switched to the visually more distinct admoniton (`!!!` or `???+`) style. This does affect editor syntax highlighting a bit and markdown linting as it's custom non-standard markdown syntax.
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| Mail Forwarding | Relay Hosts |
Introduction
Rather than having Postfix deliver mail directly, you can configure Postfix to send mail via another mail relay (smarthost). Examples include Mailgun, Sendgrid and AWS SES.
Depending on the domain of the sender, you may want to send via a different relay, or authenticate in a different way.
Basic Configuration
Basic configuration is done via environment variables:
- RELAY_HOST default host to relay mail through, empty will disable this feature
- RELAY_PORT port on default relay, defaults to port 25
- RELAY_USER username for the default relay
- RELAY_PASSWORD password for the default user
Setting these environment variables will cause mail for all sender domains to be routed via the specified host, authenticating with the user/password combination.
!!! note
For users of the previous AWS_SES_* variables: please update your configuration to use these new variables, no other configuration is required.
Advanced Configuration
Sender-dependent Authentication
Sender dependent authentication is done in config/postfix-sasl-password.cf. You can create this file manually, or use:
setup.sh relay add-auth <domain> <username> [<password>]
An example configuration file looks like this:
@domain1.com relay_user_1:password_1
@domain2.com relay_user_2:password_2
If there is no other configuration, this will cause Postfix to deliver email throught the relay specified in RELAY_HOST env variable, authenticating as relay_user_1 when sent from domain1.com and authenticating as relay_user_2 when sending from domain2.com.
!!! note To activate the configuration you must either restart the container, or you can also trigger an update by modifying a mail account.
Sender-dependent Relay Host
Sender dependent relay hosts are configured in config/postfix-relaymap.cf. You can create this file manually, or use:
setup.sh relay add-domain <domain> <host> [<port>]
An example configuration file looks like this:
@domain1.com [relay1.org]:587
@domain2.com [relay2.org]:2525
Combined with the previous configuration in config/postfix-sasl-password.cf, this will cause Postfix to deliver mail sent from domain1.com via relay1.org:587, authenticating as relay_user_1, and mail sent from domain2.com via relay2.org:2525 authenticating as relay_user_2.
!!! note
You still have to define RELAY_HOST to activate the feature
Excluding Sender Domains
If you want mail sent from some domains to be delivered directly, you can exclude them from being delivered via the default relay by adding them to config/postfix-relaymap.cf with no destination. You can also do this via:
setup.sh relay exclude-domain <domain>
Extending the configuration file from above:
@domain1.com [relay1.org]:587
@domain2.com [relay2.org]:2525
@domain3.com
This will cause email sent from domain3.com to be delivered directly.
References
Thanks to the author of this article for the inspiration. This is also worth reading to understand a bit more about how to set up Mailgun to work with this.