We have the following setup:
email sent from firstname.lastname@example.org
an imaps inbox monitoring the email@example.com
a rule that maps that email address to a "YouTrack Inbox" project (we move items out of that project and into the appropriate project once we review them)
When a user replies to an email notification sent from youtrack (for example a comment added) it is creating a new issue in the system rather than merging it into the comments of the issue that sent the notification. Is this expected? I could have sworn we had it working as I expect (merging replies into the existing issue), but I'm not sure if/what changes caused it to stop working.