[MM3-users] Whitelist in mailman3: How to allow only ~400 e-mail senders in a file whitelist to send to a list?

In mailman2, it was quite handy to place "@whitelist" into the field sender/accept_these_nonmembers, when such a file has been set up.

How can I (per list or programmatically) define the ~400 e-mail senders to be allowed to send to my about 30 lists? And, yes, I already searched for a solution of this problem, but could not find any.