If you manage an organization account on Github, you automatically get email notifications from Github about activities on your organization repos. OR you do not wish to get email notifications for your repos, you can disable email notifications on Github from your account settings.
Step 1
Login to your Github account and go to your profile settings.
Step 2
On Notifications page, you can enable/disable all kind of notifications for your profile. Here you can set your default email for email notifications.
You can enable or disable automatically watch repos and watch teams.
On Subscriptions section, you can set notifications for watching, participating, and others.
Step 3
To disable email notifications for watching, click on Notify me on Github, Email drop down and uncheck Email and Save.