Use Windows PowerShell to control how external sharing invitations can be accepted
You can use Windows PowerShell to turn external sharing on or off. Using the SharePoint Online Management Shell, administrators can now enforce new controls over how external users accept invitations. When enabled, the RequireAcceptingAccountMatchInvitedAccount parameter requires external users to accept invitations with the email account with which they originally received the invitation.
If this parameter is not set or is set to null:
When a user shares with an external user, they enter an e-mail like email@example.com, and an email is sent to Stephen at firstname.lastname@example.org. When he attempts to accept the invitation (by clicking the link in the email), he can log in with any account he wants to use. For example, he could use email@example.com, firstname.lastname@example.org, or even email@example.com. The sharing email can be forwarded and accepted by anyone. This system ensures that external users who use email aliases or who do not have a Microsoft account or organization account are able to accept the invitation.
If this parameter is set to true:
The RequireAcceptingAccountMatchInvitedAccount parameter ensures that the user who receives the invitation is also the user who accepts it. If an invitation is sent to firstname.lastname@example.org, only a user who can log into email@example.com is able to accept the invitation. Any other email account displays an error page that directs to user to use the appropriate account.
Using the SharePoint Online Management Shell, IT administrators can now require that all external sharing invitations be accepted only by the e-mail address that was originally shared with.
To enable this feature, simply run the Set-SPOTenant
cmdlet and set the “RequireAcceptingAccountMatchInvitedAccount” parameter to true.
The parameter accepts two values: True or False.
True-User must accept this invitation with firstname.lastname@example.org.
False– When a document is shared with an external user, email@example.com, it can be accepted by any user with access to the invitation link in the original e-mail.
Administrators who desire increased control over external collaborators should consider enabling this feature.
You have first to download the online management shell
Then connect use the following command
Then add the URL of the office 365 administration website
Which will be
Then you will be asked for the SharePoint credential to connect
Then run the following command
Set-SPOTenant -RequireAcceptingAccountMatchInvitedAccount $true
Set-SPOTenant -RequireAcceptingAccountMatchInvitedAccount $Null