If your email is full you can empty out your junk, spam, and sent folders to free up some space.  Here is a quick way to do that.  Be sure when you clear out those folders that you empty the "trash" folder afterwards.

You can empty entire folders easily if you are wanting to delete the entire contents of an email folder.

Click on the gear icon in the bottom left corner.

Click "manage Folders"

Click the folder you want to empty.

Click the gear icon in the bottom.

Then click "empty".