I am using GSuite (previously Google Aps) to port my gmail over to Outlook desktop version, 2016). The reason I am using GSuite is that the email address is a domain I registered through Google from enom. Everything works OK, except for the address book. It is very difficult to add a contact, and I get errors when trying to send emails to address that are not in the address book. If I try to add a contact with an email address that is not already in the address book I get the error "The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook". I get the same error when trying to send an email to an address that is not in my address book.