INBOX PAUSE is a handy pause button for your inbox. It allows you to put new messages on hold, making it so they won’t appear in your Inbox until you are ready for them. If you choose, INBOX PAUSE can notify the people who email you to let them know that their message will not be delivered to your Inbox. When you unpause your Inbox, all of the messages that you received during the break will be moved to your Inbox, and new messages will arrive as before.
This is by the same folks that created Boomerang for Gmail.