A client recently asked me to look into developing a horizontal email for one of their campaigns. I've been coding their emails for a year or so now but am unfamiliar with the best practices from a user's point of view for horizontal scroll.
This website has some examples:
From my beginning research, it looks like Apple Mail on iPhone will simply scale the email to fit the screen width. Outlook has a limit on 2000px for horizontal scroll bars, and hotmail may or may not display the email in its full width.
Is there any data or more relevant research on the pro's and cons of this approach?