Exclamation mark in email

[megajuliani]

I noticed today that there is an exclamation mark at the bottom of my email app next to the compose icon. When I click it my mail seems to go away I click it again and it reappears. Does anyone know what this icon is and how I get rid of it?

[megajuliani]

Here is a pic

[craiggiarc]

I believe this is from MailEnhancer 2.0 and it toggles between hiding read emails and showing them.

Craig