When setting up the self-service portal, by default CRM will enable users to create a local login account specific to the portal. From a management standpoint this is not the best practice since customer may have trouble logging into the portal then if the passwords expire, they forget their password, etc. Therefore, it is strongly recommended that this functionality be disabled on the self-service portal so customers are forced to use their Office 365 credentials to log into the portal. To do this follow the recommended site settings for the self-service portal as detailed here.
From here you still have the issue where customer’s created a local account to the portal. Here are the steps to take with the customer so they login with their Office 365 credentials.
- Send the customer a new invitation to the portal. See Inviting Customers to the Portal for details.
- Have them open the link in a private browser, and register for the portal again.
- Then have them login to the portal: on the login page hit Azure AD
- Then they login their Office 365 credentials.
- Moving forward customers should hit the Azure AD button to login using their office credentials.