Hello,
My suggestion is as following steps:
1. Go to the document library which will receive your e-mail.
2. Click settings-> document library settings-> Incoming e-mail settings.
3. At “E-mail attachments�part, select “save all attachments in root folder�and set “No�for “Save original e-mail�
4. Save your html format mail as a file, and load this file as an attachment for the mail, then send the mail.
Hope it can help you,
Jerry
Xing-Bing Yu