Two Minute Tip: How to enable Microsoft Teams guest access
You read how to give external users access to SharePoint, you know that Microsoft makes it easy to add guests. They just don’t always make it obvious how to do it.
You need to enable the feature that allows external users to access Microsoft Teams. You need to log in to Office 365 with administrator credentials. Navigate to the Admin Center. Expand the Settings menu and click on the Services & add-ins menu item.
The second control is labelled Turn Microsoft Teams on or off for all users of this type. It is a toggle switch and by default, it is set to Off. Click on it to toggle it to On. Click the Save button at the bottom of the panel.
You can now add guest users to Microsoft Teams
Navigate back to your Microsoft Teams site now and add your guest users. To add members to your team click on the three dots to the right of the Team name. That will drop down a menu with the option to Add members. When you click on that menu item it will open a little panel with an editable field.
Type or paste in the email address of the guest you wish to invite to the Teams space. As you type, matching names from the directory are displayed below the field. Now that we have enabled guest access, once you have entered a valid email address, you are presented with the option to add the email address as a guest. Click on the option and person will be added to the Team. You can invite several people at once. Just enter their email addresses one at a time and click Add each time. When you are done adding people, click Close.