Redmine

Hello everyone,
I have a problem with the tickets that arrive from mailboxes that don't have a redmine user. this tickets appears with anonymous author, there will be some plugin that places the author's email in some field. I have version 2.5.1 installed.
I need that user talk with admin by e-mail, adminn must seeanswer at comments. He add comment and notification goes to user .
Do somone have this plugin for this version?
Thanks =)