I’ve previously spoken about why it is important to:
PowerShell is generally the easiest manner in which that can be done. However it is possible via the Microsoft admin portal.
and select Settings from the options on the left. Then select Org settings and then Modern authentication on the right as shown above.
You should then see a dialog box appear like that shown above. At the bottom you will find the capability to enable or disable basic authentication.
If you want to disable basic authentication for the protocols listed simply unselect that option as shown above where it has been done for IMAP4 and POP3.
Before you go and disable things it is a good idea to have and see what maybe using basic authentication. You can do that by following the steps I outlined in this article:
Disabling basic authentication is a major way to improve the security of your tenant and is strongly recommended for all environments.