It does seem ironic to me. On one hand Microsoft is telling you that you can send encrypted message to any email service, and on another the recipient is being asked for an Outlook or Microsoft ID for authentication. I will ask Microsoft representative to make this point clear.

Thanks for your reply. So this is only usable if both, the sender and the recipient, use a Microsoft account and/or Office 365. That is a problem, too, as I send mail to many different people which are using different e-mail-provider.

Hi Thomas, thanks for asking this question. Recipient gets a regular looking email, with an encrypted attachment. Upon clicking on that attachment file, it fires up the browser and asks for recipient’s Office 365 ID or Microsoft Account to check for authentication.