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docker-mailserver/docs/content/config/best-practices/dmarc.md
polarathene 021e942c4c docs(refactor): Large refactor + additions + fixes
Consistency pass, formatting cleanup and fixes, introduce admonitions, add front-matter.

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docs: Add front-matter

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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.

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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.

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docs: Heading corrections

Consistency pass. Helps with the Table of Contents (top-right UI) aka Document Outline.
docs: codefence cleanup

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docs: misc cleanup

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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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Best Practices | DMARC
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DMARC Guide: https://github.com/internetstandards/toolbox-wiki/blob/master/DMARC-how-to.md

Enabling DMARC

In docker-mailserver, DMARC is pre-configured out-of the box. The only thing you need to do in order to enable it, is to add new TXT entry to your DNS.

In contrast with DKIM, DMARC DNS entry does not require any keys, but merely setting the configuration values. You can either handcraft the entry by yourself or use one of available generators (like https://dmarcguide.globalcyberalliance.org/).

Typically something like this should be good to start with (don't forget to replace @domain.com to your actual domain)

_dmarc.domain.com. IN TXT "v=DMARC1; p=none; rua=mailto:dmarc.report@domain.com; ruf=mailto:dmarc.report@domain.com; sp=none; ri=86400"

Or a bit more strict policies (mind p=quarantine and sp=quarantine):

_dmarc IN TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc.report@domain.com; ruf=mailto:dmarc.report@domain.com; fo=0; adkim=r; aspf=r; pct=100; rf=afrf; ri=86400; sp=quarantine"

DMARC status is not being displayed instantly in Gmail for instance. If you want to check it directly after DNS entries, you can use some services around the Internet such as https://dmarcguide.globalcyberalliance.org/ or https://ondmarc.redsift.com/. In other case, email clients will show "DMARC: PASS" in ~1 day or so.

Reference: #1511