I have a 2014 Mac Mini running the latest version of El Capitan. When checking my mail in the Mail app, it frequently displays a blank white space where the body of the email is supposed to be. In order to see the email, I must click the red x to close the program and then click the Mail app icon in my dock to reopen it. It seems like the problem is getting worse (more frequent). It has nothing to do with my mail accounts as it does it with all three. Has anyone else experienced this and does anyone have any suggestions to fix this? Thanks.