[easton]

It literally is, Outlook for Windows uses the IE9 engine to render HTML email, IIRC. And even then not everything is supported.

[Vinnl]

Which is an improvement over when it used to use the Word engine to render HTML email, IIRC.

[GoblinSlayer]

You aren't trying to send an angular SPA in an email, are you?

[biziclop]

Actually, it uses the Word engine for HTML rendering.