Duplicate emails now?

In the last month I'm receiving a second copy of the same email. I usually receive the second email after I close email and open it again.
Anyone having the same thing happen?
How can I prevent this from happening?Thanks, Jerry

Describe your email setup for us. There must be dozens of variations, and its important to know how you're doing it.

I can't find a name/type of our email account. I'm using the email on the dock.
Comcast is our IP.

Thanks, Jerry