In Azure Active Directory administrators may invite external parties through the B2B Guest Invitation process. A common method of inviting guests is to utilize Azure PowerShell to create the invitation. For more information on utilizing PowerShell to perform these invitations see the following.
New-AzureADMSInvitation (AzureAD) | Microsoft Docs
The invitation process allows an administrator to specify an account type as either member or guest using the switch -InvitedUserType. In the default invitation the type of account is guest.
I recently had a customer who was performing bulk provisioning of guest accounts. Their expectation is that post acceptance and account creation the user would appear in the Exchange Online global address list. These users were not appearing in the global address list. This is by design. The Exchange Online provisioning process only adds users to the global address list if the guest account type is member. In this instance the account type would need to be changed to member or the invitation removed and resent specifying the member type. Only administrators can issue invitations that contain the invited user type. End users performing invitations through related services can only invite guest type accounts.
TIMMCMIC 