Rename extraVirtualAliases to aliases and update description

The extra and virtual parts are redundant and Postfix specific and not
at all required. Compare forwards for example.

default.nix

@@ -649,7 +649,7 @@ in
       '';
     };
 
-    extraVirtualAliases = mkOption {
+    aliases = mkOption {
       type =
         let
           loginAccount = mkOptionType {
@@ -660,7 +660,6 @@ in
         with types;
         attrsOf (either loginAccount (nonEmptyListOf loginAccount));
       example = {
-        "info@example.com" = "user1@example.com";
         "postmaster@example.com" = "user1@example.com";
         "abuse@example.com" = "user1@example.com";
         "multi@example.com" = [
@@ -669,15 +668,14 @@ in
         ];
       };
       description = ''
-        Virtual Aliases. A virtual alias `"info@example.com" = "user1@example.com"` means that
-        all mail to `info@example.com` is forwarded to `user1@example.com`. Note
-        that it is expected that `postmaster@example.com` and `abuse@example.com` is
-        forwarded to some valid email address. (Alternatively you can create login
-        accounts for `postmaster` and (or) `abuse`). Furthermore, it also allows
-        the user `user1@example.com` to send emails as `info@example.com`.
-        It's also possible to create an alias for multiple accounts. In this
-        example all mails for `multi@example.com` will be forwarded to both
-        `user1@example.com` and `user2@example.com`.
+        Aliases are additional mail addresses routed to one or more existing local accounts.
+
+        The target accounts are allowed to use the alias as the sender address.
+
+        :::{note}
+        This feature is limited to local accounts and does not support LDAP or
+        other external accounts.
+        :::
       '';
       default = { };
     };
@@ -692,7 +690,7 @@ in
         the value `{ "user@example.com" = "user@elsewhere.com"; }`
         means that mails to `user@example.com` are forwarded to
         `user@elsewhere.com`. The difference with the
-        {option}`mailserver.extraVirtualAliases` option is that `user@elsewhere.com`
+        {option}`mailserver.aliases` option is that `user@elsewhere.com`
         can't send mail as `user@example.com`. Also, this option
         allows to forward mails to external addresses.
       '';
@@ -1681,5 +1679,6 @@ in
       [ "mailserver" "ldap" "postfix" "mailAttribute" ]
       [ "mailserver" "ldap" "attributes" "mail" ]
     )
+    (mkRenamedOptionModule [ "mailserver" "extraVirtualAliases" ] [ "mailserver" "aliases" ])
   ];
 }