doc: add a FAQ section

docs/faq.rst

@@ -0,0 +1,22 @@
+FAQ
+===
+
+``catchAll`` users can't send email as user other than themself
+---------------------------------------------------------------
+
+To allow a ``catchAll`` user to send mail with the address used as
+recipient, the option ``aliases`` has to be used instead of ``catchAll``.
+
+For instance, to allow ``user@example.com`` to catch all mails to the
+domain ``example.com`` and send mails with any address of this domain:
+
+
+.. code:: nix
+
+    mailserver.loginAccounts = {
+        "user@example.com" = {
+            aliases = [ "@example.com" ];
+        };
+    };
+
+See also `this discussion <https://github.com/r-raymond/nixos-mailserver/issues/49>`__ for details.

docs/index.rst

@@ -16,6 +16,7 @@ Welcome to NixOS Mailserver's documentation!
    quick-start
    setup-guide
    howto-develop
+   faq
    release-notes
 
 .. toctree::