This thing is designed to be bulletproof.
-
It uses percentages to ensure that the email is reasonably responsive without relying on hacks and unreliable tricks. Pixel widths are specified as inline-styles as a fallback just in case.
-
It works without a DOCTYPE, and is supplied with the XHTML1 Transitional DOCTYPE for reliability between the few clients that don't strip the DOCTYPE.
-
It uses only
table
,tr
,td
andbr
elements for layout, adjusted where necessary withalign
/valign
attributes. -
Attributes like
width
,height
,border
etc. are specified and then respecified in inline-style attributes, ensuring that the styling information is communicated one way or the other. -
It's composed in polyglot HTML, enabling the document to be transmitted as
application/xml+xhtml
with an amendment to thehttp-equiv
meta tag specifying the MIME type. -
It's valid XHTML1.0 Transitional!