Fix Email page for Cockpit Server Manager (#522)

* New "Copy inbound messages" label

* Fix "Configure DKIM" gui label

* Mailboxes and Addresses sections

* Move General settings for mailboxes section

Add "Shared seens" heading

* Additional options in the mailboxes settings

- Groups mailboxes disable
- Record IMAP actions
- Outlook deleted
- Max conns per user+IP

* Review fixes 1

* Major page rework for the Cockpit UI

* Fix the mail disclaimer part

* Fixes for the Filter section 1

* The Cockpit Software Center does not install optionals

* Fix Spam flag threshold label

NethServer/dev#6247

administrator-manual/en/base_system2.rst

@@ -125,6 +125,8 @@ Settings
 
 The :index:`settings` page allows the configuration of some options which could impact multiple system applications.
 
+.. _smart-host:
+
 Smart host
 ^^^^^^^^^^
 

administrator-manual/en/index.rst

@@ -71,6 +71,7 @@ Administrator Manual
 
    web_server
    firewall2
+   mail
 
 .. toctree::
    :maxdepth: 1
@@ -80,7 +81,6 @@ Administrator Manual
    disaster_recovery
    backup_customization
    backup_legacy
-   mail
    webmail
    webtop5
    pop3_connector