In the Email notifications settings tab, there are options for choosing what actions will generation an email notification. For "Issue updated" action, there's currently three sub action filters - "Note added", "Status updated", and "Priority updated".

It would be useful for our teams' use case that a sub action filter for "Category updated" be added.

We have many issues already in our database, and sometime in the middle of our project, we would like to categorize our issue in a different way. Currently, this would generate tons of emails for our developers.

I can help to develop a patch for this feature if the maintainers think this feature is worth going into the main trunk. Thanks!