To get started, sign up for a free account with the username of your choice.
Next, create an email alias for use on the service that contacts you too often. Choose an inbox name for it and decide how frequently you wish to receive the digest email.
Let's say your username is johndoe and you want to slow down your GitHub notifications to a more manageable weekly email. You can now use the following as your email:
Use your custom email address in place of your regular email address on the website or service.
Sometimes you might want to expedite your summary email. Say, you're waiting for a password reset message and need it now, you can manually trigger your digest before it's due. To do so, visit your Inboxes page when logged in and click "Get digest now" for the required alias.
To see all the available periodicities, click here.