When sending out most email Launchpad will include X-Launchpad-Message-Rationale and X-Launchpad-Notification-Type headers which you can filter with.

Bugmail

The basic rationale headers are for the cases where you are directly related to a bug:

    X-Launchpad-Message-Rationale: Assignee
    X-Launchpad-Message-Rationale: Subscriber

If you are related to a bug through a team, an @ notation is added:

    X-Launchpad-Message-Rationale: Assignee @ubuntu-kernel-bugs
    X-Launchpad-Message-Rationale: Subscriber @ubuntu-core-dev

Bug Contacts and Registrants, which are implicitly subscribed to public bugs, have their own headers:

    X-Launchpad-Message-Rationale: Bug Contact (mozilla-firefox in ubuntu)
    X-Launchpad-Message-Rationale: Registrant (kiwi)

This is combined with the @ notation when you are a member of a team who is bug contact:

    X-Launchpad-Message-Rationale: Bug Contact (ubuntu) @ubuntu-bugs

If the notification was generated in a duplicate bug, we tack on a via string:

    X-Launchpad-Message-Rationale: Assignee via Bug 1332

This one is worth explaining a bit further. Let's say this bugmail is for bug 2129; the header here means you are the assignee of "master bug" 1332, of which 2129 is a duplicate. You can use this header to filter away bug that you are receiving from duplicates of a bug you are subscribed to.

All bugmail also has:

    X-Launchpad-Notification-Type: bug

Answer Tracker Mail

The basic rationale headers are for the cases where you are directly related to a question:

    X-Launchpad-Message-Rationale: Assignee
    X-Launchpad-Message-Rationale: Subscriber

The other possibility is when you are receiving the notification because you are an answer contact for the question's target:

    X-Launchpad-Message-Rationale: Answer Contact (mozilla-firefox in ubuntu)
    X-Launchpad-Message-Rationale: Answer Contact (Ubuntu)

This is combined with the @ notation when you are a member of a team who is an answer contact:

    X-Launchpad-Message-Rationale: Answer Contact (Launchpad) @launchpad-qa

Code Hosting Mail

Mail is only sent to subscribers of branches. If you are directly subscribed to a branch the rationale header is:

    X-Launchpad-Message-Rationale: Subscriber

This is combined with the @ notation when you are a member of a team who is subscribed to the branch:

    X-Launchpad-Message-Rationale: Subscriber @ubuntu-core-dev

There are various notification types for code. When the properties of a branch are modified (for example using "Change details"):

    X-Launchpad-Notification-Type: branch-updated

When new revisions are found on a branch:

    X-Launchpad-Notification-Type: branch-revision

For notifications related to merge proposals:

    X-Launchpad-Notification-Type: code-review

Build Mail

Notifications regarding the various types of builds that Launchpad can perform for you have associated rationales. If you requested a source package recipe, live filesystem, or snap package build:

    X-Launchpad-Message-Rationale: Requester

If you created the source package (you are listed in its Changed-By field for a direct upload, or you requested a copy):

    X-Launchpad-Message-Rationale: Creator

If you did not create the source package but you signed it:

    X-Launchpad-Message-Rationale: Signer

If you did not create or sign the source package, but the build is in a PPA that you own:

    X-Launchpad-Message-Rationale: Owner

Any of these may have the @ notation appended if the relation is through a team, as above.

The notification type indicates which kind of build prompted the notification. It will be one of:

    X-Launchpad-Notification-Type: package-build-status
    X-Launchpad-Notification-Type: recipe-build-status
    X-Launchpad-Notification-Type: livefs-build-status
    X-Launchpad-Notification-Type: snap-build-status

Upload Mail

Launchpad sends notifications in response to source package uploads. If you signed a source package or requested a copy (these may be separated into distinct rationales in future):

    X-Launchpad-Message-Rationale: Requester

For primary archives, if you did not sign the source package or request the copy, but you are listed in its Maintainer field:

    X-Launchpad-Message-Rationale: Maintainer

For primary archives, if you did not sign the source package or request the copy and are not listed in its Maintainer field, but are listed in its Changed-By field:

    X-Launchpad-Message-Rationale: Changed-By

For PPAs, if you did not sign the source package or request the copy, but you have been manually configured as an additional uploader to the PPA (this is an unusual configuration):

    X-Launchpad-Message-Rationale: PPA-Uploader

Most package uploads to primary archives also cause an announcement to the appropriate -changes mailing list. This has:

    X-Launchpad-Message-Rationale: Announcement

All package upload mail also has:

    X-Launchpad-Notification-Type: package-upload