Update README.md (#2425)

Co-authored-by: casperklein <casperklein@users.noreply.github.com>

docs/content/examples/use-cases/imap-folders.md

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+---
+title: 'Use Cases | Customize Mailbox Folders'
+hide:
+  - toc # Hide Table of Contents for this page
+---
+
+# Mailboxes (_aka IMAP Folders_)
+
+`INBOX` is setup as the private [`inbox` namespace][dovecot-docs-namespaces]. By default [`target/dovecot/15-mailboxes.conf`][gh-config-dovecot-mailboxes] configures the special IMAP folders `Drafts`, `Sent`, `Junk` and `Trash` to be automatically created and subscribed. They are all assigned to the private [`inbox` namespace][dovecot-docs-namespaces] (_which implicitly provides the `INBOX` folder_).
+
+These IMAP folders are considered special because they add a [_"SPECIAL-USE"_ attribute][rfc-6154], which is a standardized way to communicate to mail clients that the folder serves a purpose like storing spam/junk mail (`\Junk`) or deleted mail (`\Trash`). This differentiates them from regular mail folders that you may use for organizing.
+
+## Adding a mailbox folder
+
+See [`target/dovecot/15-mailboxes.conf`][gh-config-dovecot-mailboxes] for existing mailbox folders which you can modify or uncomment to enable some other common mailboxes. For more information try the [official Dovecot documentation][dovecot-docs-mailboxes].
+
+The `Archive` special IMAP folder may be useful to enable. To do so, make a copy of [`target/dovecot/15-mailboxes.conf`][gh-config-dovecot-mailboxes] and uncomment the `Archive` mailbox definition. Mail clients should understand that this folder is intended for archiving mail due to the [`\Archive` _"SPECIAL-USE"_ attribute][rfc-6154].
+
+With the provided [docker-compose.yml][gh-config-dockercompose] example, a volume bind mounts the host directory `docker-data/dms/config/` to the container location `/tmp/docker-mailserver/`. Config file overrides should instead be mounted to a different location as described in [Overriding Configuration for Dovecot][docs-config-overrides-dovecot]:
+
+```yaml
+volumes:
+  - ./docker-data/dms/config/dovecot/15-mailboxes.conf:/etc/dovecot/conf.d/15-mailboxes.conf:ro
+```
+
+## Caution
+
+### Adding folders to an existing setup
+
+Handling of newly added mailbox folders can be inconsistent across mail clients:
+
+- Users may experience issues such as archived emails only being available locally.
+- Users may need to migrate emails manually between two folders.
+
+### Support for `SPECIAL-USE` attributes
+
+Not all mail clients support the `SPECIAL-USE` attribute for mailboxes (_defined in [RFC 6154][rfc-6154]_). These clients will treat the mailbox folder as any other, using the name assigned to it instead.
+
+Some clients may still know to treat these folders for their intended purpose if the mailbox name matches the common names that the `SPECIAL-USE` attributes represent (_eg `Sent` as the mailbox name for `\Sent`_).
+
+### Internationalization (i18n)
+
+Usually the mail client will know via context such as the `SPECIAL-USE` attribute or common English mailbox names, to provide a localized label for the users preferred language.
+
+Take care to test localized names work well as well.
+
+### Email Clients Support
+
+- If a new mail account is added without the `SPECIAL-USE` attribute enabled for archives:
+    - **Thunderbird** suggests and may create an `Archives` folder on the server.
+    - **Outlook for Android** archives to a local folder.
+    - **Spark for Android** archives to server folder named `Archive`.
+- If a new mail account is added after the `SPECIAL-USE` attribute is enabled for archives:
+    - **Thunderbird**, **Outlook for Android** and **Spark for Android** will use the mailbox folder name assigned.
+
+!!! caution "Windows Mail"
+
+    **Windows Mail** has been said to ignore `SPECIAL-USE` attribute and look only at the mailbox folder name assigned.
+
+!!! note "Needs citation"
+
+    This information is provided by the community.
+    
+    It presently lacks references to confirm the behaviour. If any information is incorrect please let us know! :smile:
+
+
+[docs-config-overrides-dovecot]: ../../config/advanced/override-defaults/dovecot.md#override-configuration
+[gh-config-dockercompose]: https://github.com/docker-mailserver/docker-mailserver/blob/master/docker-compose.yml
+[gh-config-dovecot-mailboxes]: https://github.com/docker-mailserver/docker-mailserver/blob/master/target/dovecot/15-mailboxes.conf
+[dovecot-docs-namespaces]: https://doc.dovecot.org/configuration_manual/namespace/#namespace-inbox
+[dovecot-docs-mailboxes]: https://doc.dovecot.org/configuration_manual/namespace/#mailbox-settings
+[rfc-6154]: https://datatracker.ietf.org/doc/html/rfc6154