Hi, I'm Randy. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.
Your email server settings need to be correct for the Email app on Kindle Fire to send and receive emails. Contact your email service provider for more information about the server settings needed to setup your email.
If your service provider's email settings have changed, you may need to reconfigure the settings in the Email app.
Did that with for you?