Mail merge from Hotmail using list in Excel

I am a new Hotmail user. I set up an account for a non-profit organization I
am involved in. I want to send an introductory email to an existing list of
contacts/email addresses in an Excel spreadsheet.

Mail merge is so easy from Outlook. Is it impossible from Hotmail?

I downloaded and installed a piece of software called Webmail Assistant that
claimed to make it possible. However, its "compose" form is erroring. I
suspect the software is not compatible with Windows Vista. (They only claim
compatibility with XP, but I decided to try it anyway.)