There isn't an on/off switch for this in filemaker, as there is no direct integration to office365.
LDAP lookup also isn't supported by office365.
Microsoft recommends to people needing LDAP functionality while using office365 to setup an on-premises active directory server that uses DirSync to sync users into activedirectory. Filemaker could then use external authentication to that AD server to allow logins.
There may be a homebrewed solution that you can create using REST or some other API to authenticate credentials to the office365 server, and then keep a mirrored copy in a users table in FileMaker. If you go that route, the accounts module is a good place to start for table based user-management in filemaker:
You might also want to use the work we did on the WebDirect URLs, which allow you to use PHP directly with WebDirect to create/store/pass PHP session variables into filemaker.
Combinations of the above two techniques may allow you to put something together, however I am not familiar enough with the Office365 available APIs/SDKs to give further advice. But it does appear that there is REST functionality at least:
Thank you for your reply. As company grow, company own Active directory role becomes less important when we started to use Office365 email system. At the IT admin, we want to reduce user difficult to remember password and keep company own system privacy without too much impact from downtime cloud based service.
Currently we try to balance two ways and thank you for your input.
I think I will feedback to FileMaker Pro to enhance such FileMaker Pro server with these cloud authentication feature with single page enable within system. (Google and Microsoft Office 365). I believe it will accelerate more people using it.
As I noted, you can most likely do it from within the current filemaker feature set. I doubt filemaker would consider this type of authentication as part of it's feature set. There would probably be too many variables out of their control that would make it unviable. LDAP has been around for years and hasn't changed much. Meanwhile what you can get from the other side of a REST API is constantly changing.
It sounds like you just need a good password manager, like the keychain in OSX, to make your user's lives a bit easier.