I need to be able to make HTML custom emails with div tags, formatting, and such, and I need to be able to send it with Outlook 2010.
How is this possible?
You can install HTML Code Editor for Outlook.
You can download a installer on download tab. It'll allow you to import HTML file or edit HTML source code of your e-mail.
I'm running Outlook 2007, not 2010, but the instructions here worked for me:
Be aware that the HTML Outlook generates is at least as ugly as any of the auto-generated stuff from any Microsoft application.