This tenant "adomain.com" does not allow email verified users to be added due to an admin-defined policy. Contact tenant's admin to report the error.
Install Microsoft Azure Active Directory Module
Download the MSI at the following link: http://connect.microsoft.com/site1164/Downloads/DownloadDetails.aspx?DownloadID=59185
Connect to Azure
Run the following command, and enter your credentials for Azure AD:
Change Company settings to allow Email Verification
Set-MsolCompanySettings -AllowEmailVerifiedUsers $true