This problem only appears on computers (not on smart phones or tablets), and usually on older computers that are running older email programs, like AOL or Outlook Express.
The emails are sent in HTML, and sometimes the HTML code does not render correctly on certain computers.
To fix this to can change the "Email Format", here is how you do this:
On your computer, on your Home Page, click on Edit Settings in the top left of the page, click on Privacy Settings, and then switch your Email Format from HTML to Plain Text.
By doing this, all future emails will be sent in a plain text format so you will be able to read them.