I'm having an issue I can't seem to fix or find a solution online.

When sending emails to myself in PHP, using codeigniter's built in email class, my emails are coming up blank in the Windows 8 mail app, however it shows normal on my web based email. I've tried different email accounts but it all does the same thing. I thought part of it was the email being too long, seeing as I used to load most of the site's css into the head of the html, but even when taking that out and using inline styles, it still shows up blank, any ideas? The only external source I'm using is the site logo in the top of the email, but I don't see why that would pose an issue for the mail app, especially considering I remember seeing messages to "click here to reveal images" in the app.

Also, in regards to the logo, is it possible to send it as an attachment instead rather than an external link? I've seen this done before as well. If not, what are the other alternatives besides just typing the website name out? I want to include the logo if possible.