A week ago Microsoft released the public preview of the Azure B2B invitation API. I have seen this at Ignite in September that they were working on that. The announcement can be found here https://blogs.technet.microsoft.com/enterprisemobility/2016/10/31/azuread-b2b-invitation-api-is-now-in-public-preview/
With this announcement I went looking into this what other options there already are for inviting a partner into your AD. The options at this moment are:
- Upload CSV file thru https://manage.windowsazure.com
- Add a user in the new portal https://portal.azure.com
- Invitation API in the Microsoft Graph
With these three options you have a way for every kind of administrator. The csv function is a simple way to invite a larger group of users, but not the easiest one to work with. The UI in the new portal is a lot easier and integrates with adding a normal user to your AD. When the input recognizes a username with a domain not known to the Azure AD it will ask to add a personal invite message and will send an invite to that user.
This gives a uniform input for internal and external users.
With the use of the invitation API you are able to do some customizations like adding people in the CC for the invitation email, see the first link to the announcement for all the option.
When you share from SharePoint, the person receiving the invite can choice for organization account and will authenticate with that. When that same person has also a Microsoft account, you are not able to control what account the invited user uses. If you want to control that you need to invite that user thru Azure AD