Added README section for vpopmaild driver at the password-plugin

plugins/password/README

@@ -42,6 +42,7 @@
  2.16. DBMail (dbmail)
  2.17. Expect (expect)
  2.18. Samba (smb)
+ 2.19. Vpopmail daemon (vpopmaild)
  3. Driver API
 
 
@@ -299,6 +300,16 @@
  Driver to change Samba user password via the 'smbpasswd' command.
  See config.inc.php.dist file for configuration description.
 
+ 2.19. Vpopmail daemon (vpopmaild)
+ -----------------------------------
+
+ Driver for the daemon of vpopmail. Vpopmail is used with qmail to
+ enable virtual users that are saved in a database and not in /etc/passwd.
+
+ Set $rcmail_config['password_vpopmaild_host'] to the host where vpopmaild runs.
+
+ Set $rcmail_config['password_vpopmaild_port'] to the port of vpopmaild.
+
 
  3. Driver API
  -------------