The recipient can have any email account. The sender needs to have a Microsoft account. It can be an Office365 subscription which can have your own company domain if you want.

This was from 2020
"Office 365 is used by over a million companies worldwide, with over 650,000 companies in the United States alone using the office suite software."

What a lot of investors don't know is I believe you can also have one of the below accounts below to send out verbMAIL since they all use the same browser based outlook tool. I've tested it with O365 and Hotmail and it works the same.

@outlook.com
@hotmail.com
@live.com
@msn.com
@passport.com
@passport.net

Now keep in mind if you had a different email account than above like gmail, you could forward the email to that account and send it out which takes 10 seconds. I can do that both with yahoo and gmail.