Creating a large e-mail group quickly

First create groups in contacts with the help of this article : Contacts (El Capitan): Create a group in Contacts

Then , you can mail to groups take a glance at this article : Mail for Mac: Address messages in Mail

Use a group address

If you create groups in the Contacts app—say for a book club or cycling team—you can send messages to everybody in the group at once.

Type the name of a group in the address field of your message.Either the group or individual contacts are shown. If the group is shown but you want to see individual contacts instead, click the arrow next to the group name, then choose Expand Group.

Open address book via spotlight , took cursor on File > New group from selection .

Sending to a large group of people from you local mail account is problematic. Many isps limit you to so many emails per day. It's working for you so far, so it most be ok for you. There are a number of mass marketing email providers. I use mailchimp. You can send so may mailings per month or some such limit. I have a mailing of 100+ people. [ Which reminds me that I need to do a mailing. 😉 ]

They allowed some file upload of names to get you started I seem to recall.

R