I have several group email contact lists in Outlook on my laptop PC. For a long time, I was unable to create this functionality on my Apple devices, but after recent research, I found the solution.
Create the Group List
Add a new Contact and use an appropriate name to help you recognize the Contact is a group email list.
Tap the add email button.
Tap home, if you wish, and choose Add a Custom Label, to further help you identify the list.
Add the individual email addresses in the email field and separate them with commas.
Tap Done in the upper right corner of the contact when you’ve added all email addresses.
Using the List
Normally, when you send an email message, you type the Contact name or email address into an address box. This method does not work for a group list. While Mail will find the group email contact, you’ll receive an “invalid email address” error when you send the message. Instead, open the Contacts app, find the group email contact, and tap its Mail button. The Mail app opens with all addresses populated in the To: field. Type your subject and message and send.
Tips
You do not need an individual contact entry for every address in the group email list.
Tap the To: address field and it expands to show all addressees. You can then tap individual addresses and delete them if needed.
If everyone on your group list does not know everyone else, protect their privacy. Tap the To: field to expand the list. Then tap the first or last address and drag the selector handles to highlight all addresses. Cut them and Paste them into the BCC: field. This prevents email addresses from being exposed to all recipients.