Blank html email delivered

I'm sending an email from a website. It renders fine in Gmail, Outlook, Android, iPhone/iPad...but NOT Apple Mail (Yosemite). I've tried to modify the headers but it doesn't seem to matter. I'm using mailgun at the moment as the sender in case that may matter. Here's a few of the headers...

(For testing I'm also sending a text/plain format with a single line to see if it made a difference.)

Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable


Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable

And this is the strangest part, I've never encountered this. This is what the HTML looks like when viewing the source in Apple Mail:

<table cellpadding=3D"0" cellspacing=3D"0" border=3D"0" align=3D"center" =
width=3D"700">

The entire email is blank. I don't even see the one testing line from plain text. Apple Mail is hooked up to a GMail account. The message appears fine when viewing in GMail.