What is Webmail Ad Blocker?
Block ads on the right side of the screen when using Gmail, Yahoo Mail, Hotmail and Outlook.com which expand your message space
Removes the ads and sponsored links and squeezes out the empty space left behind by other ad blockers to give you more room to write your messages.
There are also options to hide various other items on your Google Mail page to make it more zen.
Webmail Ad Blocker Screenshots
Webmail Ad Blocker information