It would be useful if JIRA added some more headers to messeges sent. It will make easier to created filters on mail clients.

For example, I'd like to automatically archive emails JIRA sends me relative to the xdoclet project, but not to the xdocletgui project. In the current setup, the only way to differentiate these messages is searching the Topic field. This is not optimal.

So, let's suppose I create a field in my email message that looks for emails:

1) Sent by legendaryservice@atlassion.com
2) Topic starts with [JIRA]
3) Topic contains XDT (the project key)

You see, there are two criteria based on topic. Not good. JIRA could add some custom header (like X-Jira-Project) to emails sent, so I could set up a filter based on that.