Use your web-based Outlook.com (aka Hotmail.com).
It has a feature to create a group > give it a name > enter group members' addresses into the group.
Once done, next time you want to send an email to all the group members, just click the group name into the TO box > compose your message > click Send.
That's it. Each group member will receive the same email.
If you need in-depth instructions to create Group, please post back.
P.S. I do not know if the Mail app in Windows 10 can do that too. I don't use it and I won't bother to check it out. Maybe it has a similar feature too.