After installing IE 11 Preview my Zoom setting (150%) does not work for Live Mail responses.  Replying to a received email I have to block the received email and change the font to 18 to be able to see it and my replay has to be set to 18 [plain text - no formatting] to be able to see what I am writing.  Yes,  I wear glasses but I have them on. This problem was fixed in about 2 months in Outlook (it had the same problem - Zoom did not carry through when a respose was to be entered to a received message.) I reported the problem in Outlook calling it "Zoom not sticking in responses to email".

I would estimate the font size currently in a response is less then 6 points.