Bug Tracking Email Interaction

I'd like for my users to not only create bugs/issues/tickets, but I'd like for them to be able to respond to the notifications and have those responses appended to the bug as a comment. Much the same way that notes are appended to in tasks.

I don't want to lose track of any information that the clients provide. Currently, their responses only go directly to the project manager, and are not automatically made a part of the issue.