Can a user respond to an emailed thread via the email?

This may be just a clarification for me.

The question's context is about a private group (which will come as pages in EasySocial in December). Many users in a private group I want to create mainly use email, and I want to know if a user can reply to a thread via email? In other words, when a member of a group (page) receives an email with a discussion topic, or a reply to the discussion topic, can that member then reply to the email and have his reply be automatically posted to the thread in EasyDiscuss on my site?

This question applies even now with any EasyDiscussion topic. Once a user checks that they want to subscribe to a topic, can they reply to the topic via email?

Thanks
Peter