Fix the rst syntax for most documentation

docs/configuration.rst

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+Mailu configuration settings
+============================
+
+Common configuration
+--------------------
+
+The ``SECRET_KEY`` **must** be changed for every setup and set to a 16 bytes
+randomly generated value. It is intended to secure authentication cookies
+among other critical uses.
+
+The ``DOMAIN`` holds the main e-mail domain for the server. This email domain
+is used for bounce emails, for generating the postmaster email and other
+technical addresses.
+
+The ``HOSTNAMES`` are all public hostnames for the mail server. Mailu supports
+a mail server with multiple hostnames. The first declared hostname is the main
+hostname and will be exposed over SMTP, IMAP, etc.
+
+The ``POSTMASTER`` is the local part of the postmaster email address. It is
+recommended to setup a generic value and later configure a mail alias for that
+address.
+
+The ``AUTH_RATELIMIT`` holds a security setting for fighting attackers that
+try to guess user passwords. The value is the limit of requests that a single
+IP address can perform against IMAP, POP and SMTP authentication endpoints.
+
+Mail settings
+-------------
+
+The ``MESSAGE_SIZE_LIMIT`` is the maximum size of a single email. It should not
+be too low to avoid dropping legitimate emails and should not be too high to
+avoid filling the disks with large junk emails.
+
+The ``RELAYNETS`` are network addresses for which mail is relayed for free with
+no authentication required. This should be used with great care. It is
+recommended to include your Docker internal network addresses if other Docker
+containers use Mailu as their mail relay.
+
+The ``RELAYHOST`` is an optional address of a mail server relaying all outgoing
+mail.
+
+The ``FETCHMAIL_DELAY`` is a delay (in seconds) for the fetchmail service to
+go and fetch new email if available. Do not use too short delays if you do not
+want to be blacklisted by external services, but not too long delays if you
+want to receive your email in time.
+
+The ``RECIPIENT_DELIMITED`` is a character used to delimit localpart from a
+custom address part. For instance, if set to ``+``, users can use addresses
+like ``localpart+custom@domain.tld`` to deliver mail to ``localpart@domain.tld``.
+This is useful to provide external parties with different email addresses and
+later classify incoming mail based on the custom part.
+
+The ``DMAR_RUA`` and ``DMARC_RUF`` are DMARC protocol specific values. They hold
+the localpart for DMARC rua and ruf email addresses.
+
+Web settings
+------------
+
+The ``WEB_ADMIN`` contains the path to the main admin interface, while
+``WEB_WEBMAIL`` contains the path to the Web email client.
+
+Both ``SITENAME`` and ``WEBSITE`` are customization options for the panel menu
+in the admin interface, while ``SITENAME`` is a customization option for
+every Web interface.
+
+Advanced settings
+-----------------
+
+The ``PASSWORD_SCHEME`` is the password encryption scheme. You should use the
+default value, unless you are importing password from a separate system and
+want to keep using the old password encryption scheme.