We can only email people we have an address for. Everyone else gets the invite from you, and your event page says how many are left: 4 people with no email haven't answered.
The quickest way is one message to all of them. Share the link opens your phone's share sheet with the invite written and the event's link at the end, so you can send it once to a group chat, WhatsApp, or several people in Messages. Where the browser has no share sheet, most computers included, the button is Copy message.
That one link works for everyone on your list, even with public replies off: each person answers by typing the mobile or email you have for them, and the answer lands on their own row, counted once. Someone you have no mobile or email for is found by their first name, as long as nobody else on the list without contact details shares it.
To reach people one at a time, tap the count. The sheet lists them, each with a Text button that opens your Messages with the invite and that person's own link. It goes from your number, as your message. Someone with no mobile has Copy link instead.
Each row shows where that person is: texted, said yes, said no or not sure. Text ticks a person off for you; tick them by hand if you reached them another way. Once they answer, they move under Answered.
Their own link is on their row on the event page too, under Copy link. Never forward one guest's own link to someone else: an answer on it comes back under that guest's name. Press Invite and add the new person instead.