For some time I have endured with the font size changing whilst in the middle of writing an email.  This often happens when I hit the ENTER tab but also when I paste an emotion into the email.  It is particularly annoying and means that I have to highlight the document and then change the font for all of the text to get it right.

Is there a way of formatting this so that this does not occur?  Well written software which has been around for so long should not have such a fundamental flaw.