Comcast

Comcast strips your doctype. There is no known workaround for this.

On wide emails, you may occasionally see an email that looks like it is hanging off the right side of the frame. In our web client previews (Yahoo! Mail, Outlook.com, AOL Mail, Gmail, etc), we intentionally modify the client’s styles to allow your entire email to be visible even if it is wider than the viewing pane. We do this because we can’t account for all of the possible email widths that may come through our system. No, this is not exactly what it would look like in the live client, but it enables you to see the whole email, as well as how much of the email would require horizontal scrolling to view. The part of your email that overlaps the right column would not normally be visible in a browser window of that width.