How do I do a mail merge on mac using mac mail (I do not have outlook)

HI Guys

I hope one of you can help me, I have Word and Excel (I do not have Pages).

I have Mail (macs email program) and do not have Outlook.

I now need to send an email merge to a list of people. I have put their details into excel and have created the email in word however the button I need to click in word to generate email is grey out.

Watching videos on how to do a mail merge they all appear to use word and outlook. However that is not an option for me as I do not have outlook so I am hoping there is some other way maybe I need to use automator?

Any suggestions would be gratefully accepted as if I have to send these all manually it will take me forever.