All your Kindle devices have a Kindle e-mail address. If your telephone or iPad has a Kindle app in it, it too has been assigned a Kindle e-mail. To find your device’s Kindle e-mail address, do the following.
Go into the Amazon site and click on your “Accounts and Lists.”
Click on “Your Devices and Content.
Click on “Change your digital and device settings.”
Scroll down to “Personal Document Settings.”
Under this heading, you will see the email addresses assigned to all your devices (Kindle Fire, Kindle Paperwhite, etc. If you have other devices not Kindle but that have the Kindle app installed, they too will have assigned email addresses. For example, my iPad has a Kindle address because I have a Kindle app registered on it.
Find the Kindle address for the device where you want to send your Mobi file. Write it down exactly as you see it. By the way, now is the time to change that email address if you want one easier to memorize. Just hit the edit button at the far right. You can change both the name of the device and the email. the @kindle.com must remain.