Share files with external user in SharePoint online

Question

When you share a PDF file which is inside a SharePoint online directory with a External User (those that use a Micrososft account not those that use organizational account from another tenant).

Does it mean that the user has been added to your Azure AD automatically?

Answer 1

Yes, and they show up as active (Unlicensed) users in you Admin Center [https://portal.office.com/adminportal/home#/users].

You will see them with their full e-mail address (@-sign changed to underscore _) like this:

name.lastName_gmail.com#EXT#@tenantName.onmicrosoft.com

So technically they are a part of Azure AD which controls authentication in you Office 365 tenant.