@Leonardo Alano16 thanks Leo for the comment. You are amazing :)
@Katie Barnes12 If you are not using SendGrid, you are able to send up to a specific number of invitations each day, which is different for each plan:
Free Plan: 500/day
Premium Trial: 500/day
Plus Plan + Premium Plan: 1000/day
Enterprise Plan: 10,000/day
Please be advised that without SendGrid, there is a chance for the emails to end up in spam.
Now, if you install the SendGrid app6, you will make sure that your community emails never end up in spam. However, if you are on SendGrid's free plan, you have the limitation on the number of the email you can send each month. You can upgrade your plan in Sendgrid to increase this number.