Scheduling: Email correspondences are stretching awkwardly. Code fix?

Site URL: http://originswithin.com

My client is paying for the scheduling feature and all emails from this feature render horribly (attached screenshot). I looked at the code and it looks like the width is supposed to be 500px max. It never looks right as some of the items are flush left  to the edge of the email window and I have to scroll to see all of the content some is flush left. The only info I changed was adding a logo image and some text at the bottom of the email. A smaller window pane still cuts off information

Any help/code to contain this to one column of space that is 600 px or less would be so appreciated.

EDIT: It looks fine on a phone. I am using the Mail app on a Mac. Is this a mail client issue? Thanks