Here’s a nice little Easter egg for you, Mailbox users. You can get an additional 1GB of storage for free by simply linking your Mailbox account with Dropbox.
To activate this, you just need to head to the Settings menu on your Mailbox iOS app, select Dropbox, and then add your account information. If your accounts are already linked you just need to unlink them and reconnect to get that free 1GB.
Source: The Next Web