When adding users to a group in Microsoft 365 Admin the choices are limited to the list of users in the directory. This is typically limited to members of the organization, but external users can be added to the directory as what are called Guest users.
The option for adding Guest users is available in the File Share/Team Access Request form. Guest users will be added to the Directory as part of one of these requests.
Receive invitation to join as a Guest
When guests are added to the Directory they receive an invitation email and can be added to Teams. When a guest is invited to a team they get an additional welcome email. This email includes information on the team they were added to and has links to various resources for the group.
View the SharePoint Online Site and Team Documents
Follow the link in the invite email labeled Go to SharePoint.
You'll be directed to sign in with your account. If you've signed in previously but don't remember your password, click the Can't access your account? option to reset your password.
After signing in, you'll be asked to grant permission. This will confirm what data Adler will be able to see when you collaborate with a Team. Select Accept to continue.
You will be taken to the Home page of the SharePoint Online Site. This is a good spot to bookmark to return to the site regularly. Navigate to the Documents page to see the Team documents.
View emails sent to the Team
As a member of a team with email enabled, you will receive email sent to the team in your inbox.
Email sent to the Team will have the Team email in the to: field. We recommend making a label specifically for emails sent to the Team. You can call it anything you like including the Team or the University name. In this example, I've named the label Adler. Grab the Team email address in the to: field and make a filter so anything sent to this email address gets the label.