There are a few ways that you might find yourself receiving email updates about a bug that’s tracked in Launchpad. Usually, it’s because you reported the bug, commented on it, subscribed directly to the bug report or you subscribed to all bugs associated with a particular project or distro.
Alongside the information in the body of the email, Launchpad adds headers that give you extra details. Those headers are particularly useful if you want to filter certain emails.
Recently, Gavin added a new header to Launchpad bug mails:
It lists each person who has left a comment on the bug, including the original poster, with each name separated by spaces.