I did some searching but didn't turn up any suggestions for this so wanted to at least get it out there.

It would be very useful to have a "Find Related" feature in webmail similar to Outlook. I've used that feature in Outlook often to find my reply to a message to verify what I said and when I sent it.

Adding a "Find Related" option to the right click menu (near "Move") of an email message (and the Actions button menu) that when clicked would show the related messages as if they were search results would be perfect.

Functionally, the easiest solution would be to just search for messages (in all folders) that shared the same subject but SM may have a better idea on what attributes are available to match.