Whenever there has been a change made to one particular project you own or collaborate on, you will receive a summary email. You can also receive an email each time you're mentioned in a comment in a particular project. 

These emails are known as Digests and Mentions and are sent every 15 minutes if there is any new activity that you haven’t been notified about yet. 

They can be disabled and enabled from the Settings tab of each of the projects you participate on.

Please beware that this will only turn-off/on the notifications for that individual project. 

If you want to edit the notification settings for more than one project, you will need to follow the same steps for each of them.