You can manage notifications in your personal notification settings. Note that there are options for workflow notifications that are separate from options for project alerts. Selecting "default" means that project will follow the top level project filter.
In the body of each email you will see the specific reason you are receiving that email.
Select Unsubscribe to stop receiving emails for this issue.
You will automatically be subscribed to an issue when taking one of the following actions:
You can unsubscribe from a particular issue by selecting that issue and clicking the Unsubscribe button.