replyPUSH

Much like WordPress.com’s “Comment Reply via Email”, you can reply to any post you subscribe to.
Integrates with the wonderful <a href="https://wordpress.org/plugins/subscribe2/" title="subscribe2" rel="ugc">subscribe2</a> and <a href="http://replypush.com" title="replyPUSH.com" rel="nofollow ugc">replyPUSH.com</a> service to provide the email reply magic.
It automatically adds notifications for comment posts to keep the conversation flowing 🙂
All the subscriber need do, is reply at the top of their quoted email notification.

Reply By Email

Allows your users to reply to articles / blog posts and comments via email.

Boone Gorges

Add a Title field to bbPress replies. Requires bbPress.
Originally developed for <a href="http://mcnrc.org/" rel="nofollow ugc">mcnrc.org at LaGuardia Community College, CUNY</a>.

Reply By Email vs bbPress Reply Titles