docs: Improve cron tasks and fix link in documentation (#2708)

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>

docs/content/config/advanced/full-text-search.md

@@ -103,6 +103,42 @@ While indexing is memory intensive, you can configure the plugin to limit the am
     ```
     docker-compose exec mailserver doveadm fts optimize -A
     ```
+    Or like the [Spamassassin example][docs-faq-sa-learn-cron] shows, you can instead use `cron` from within `docker-mailserver` to avoid potential errors if the mail-server is not running:
+
+??? example
+
+    Create a _system_ cron file:
+
+    ```sh
+    # in the docker-compose.yml root directory
+    mkdir -p ./docker-data/dms/cron # if you didn't have this folder before
+    touch ./docker-data/dms/cron/fts_xapian
+    chown root:root ./docker-data/dms/cron/fts_xapian
+    chmod 0644 ./docker-data/dms/cron/fts_xapian
+    ```
+
+    Edit the system cron file `nano ./docker-data/dms/cron/fts_xapian`, and set an appropriate configuration:
+
+    ```conf
+    # Adding `MAILTO=""` prevents cron emailing notifications of the task outcome each run
+    MAILTO=""
+    #
+    # m h dom mon dow user command
+    #
+    # Everyday 4:00AM, optimize index files
+    0  4 * * * root  doveadm fts optimize -A
+    ```
+
+    Then with `docker-compose.yml`:
+
+    ```yaml
+    services:
+      mailserver:
+        image: docker.io/mailserver/docker-mailserver:latest
+        volumes:
+          - ./docker-data/dms/cron/fts_xapian:/etc/cron.d/fts_xapian
+    ```
+
 
 ### Solr
 
@@ -153,3 +189,5 @@ However, Solr also requires a fair bit of RAM. While Solr is [highly tuneable](h
 #### Further Discussion
 
 See [#905](https://github.com/docker-mailserver/docker-mailserver/issues/905)
+
+[docs-faq-sa-learn-cron]: ../../faq.md#how-can-i-make-spamassassin-better-recognize-spam

docs/content/config/environment.md

@@ -759,7 +759,7 @@ you to replace both instead of just the envelope sender.
 - **empty** => no default
 - password for default relay user
 
-[docs-faq-onedir]: ../faq.md#what-is-the-mail-state-folder-for
+[docs-faq-onedir]: ../faq.md#what-about-docker-datadmsmail-state-folder-varmail-state-internally
 [docs-tls]: ./security/ssl.md
 [docs-tls-letsencrypt]: ./security/ssl.md#lets-encrypt-recommended
 [docs-tls-manual]: ./security/ssl.md#bring-your-own-certificates

docs/content/faq.md

@@ -184,23 +184,25 @@ The following configuration works nicely:
     # This assumes you're having `environment: ONE_DIR=1` in the env-mailserver,
     # with a consolidated config in `/var/mail-state`
     #
+    # '> /dev/null' to send error notifications from 'stderr' to 'postmaster@example.com'
+    #
     # m h dom mon dow user command
     #
     # Everyday 2:00AM, learn spam from a specific user
     # spam: junk directory
-    0  2 * * * root  sa-learn --spam /var/mail/example.com/username/.Junk --dbpath /var/mail-state/lib-amavis/.spamassassin
+    0  2 * * * root  sa-learn --spam /var/mail/example.com/username/.Junk --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     # ham: archive directories
-    15 2 * * * root  sa-learn --ham /var/mail/example.com/username/.Archive* --dbpath /var/mail-state/lib-amavis/.spamassassin
+    15 2 * * * root  sa-learn --ham /var/mail/example.com/username/.Archive* --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     # ham: inbox subdirectories
-    30 2 * * * root  sa-learn --ham /var/mail/example.com/username/cur* --dbpath /var/mail-state/lib-amavis/.spamassassin
+    30 2 * * * root  sa-learn --ham /var/mail/example.com/username/cur* --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     #
     # Everyday 3:00AM, learn spam from all users of a domain
     # spam: junk directory
-    0  3 * * * root  sa-learn --spam /var/mail/not-example.com/*/.Junk --dbpath /var/mail-state/lib-amavis/.spamassassin
+    0  3 * * * root  sa-learn --spam /var/mail/not-example.com/*/.Junk --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     # ham: archive directories
-    15 3 * * * root  sa-learn --ham /var/mail/not-example.com/*/.Archive* --dbpath /var/mail-state/lib-amavis/.spamassassin
+    15 3 * * * root  sa-learn --ham /var/mail/not-example.com/*/.Archive* --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     # ham: inbox subdirectories
-    30 3 * * * root  sa-learn --ham /var/mail/not-example.com/*/cur* --dbpath /var/mail-state/lib-amavis/.spamassassin
+    30 3 * * * root  sa-learn --ham /var/mail/not-example.com/*/cur* --dbpath /var/mail-state/lib-amavis/.spamassassin > /dev/null
     ```
 
     Then with `docker-compose.yml`: