The Enterprise edition also allows for enabling email-only login. In this setup, a user will only login with their email address, and no password. Once they enter their email address, it will send them a temporary link that will log them in to the system.

This can be useful if otherwise connecting to an organization's authentication system is deemed too difficult or impractical.

This can be enabled (admin only) in the Configuration / Authentication Settings area by setting Allow Email Login to Yes. Once this is set, a user can login using just their email address and no password. It will then email them with a temporary link to login. The user must be pre-registered in the system. 

This option can be switched off at any point, but doing so will require that user's reset their passwords before logging in (unless they are using AD or SSO).

Email-only login can be used in conjunction with SSO. Users who login with SSO can only login with SSO from that point onwards. Users who have not logged-in with SSO can use the email login to gain access.