using this feature with various usernames gives me no error. the problem is when i use the same username. for example :
firstname.lastname@example.org -> email@example.com
firstname.lastname@example.org -> email@example.com
firstname.lastname@example.org -> email@example.com
firstname.lastname@example.org -> email@example.com
user1 doesn't work. it only sends emails to the first forwarding rule created. other users works ok.