You must have “Pop-ups” enabled in your Web Browser to see the entire message by double-clicking on it.
In Internet Explorer, select “Tools” > “Pop Up Blocker” > ”Always Allow Pop Ups from this site” or, if the option to "Always Allow Pop ups" is not available from this part of the menu, select “Tools” > “Pop Up Blocker” > ”Settings” and add the current URL to the “Always allow Pop-ups” site list.
Some custom toolbars, such as Alexa and Google have their own layer of Pop-up blocking functionality. Follow specific instructions in the help documentation for the custom toolbar to disable Pop-up blocking for the URL of your Outlook Web Access installation.
Note: It is highly recommended that Internet Explorer be the browser used for Outlook Web Access