Email bindings
Settings > Sign-in > Email bindings lists the e-mail addresses that an administrator has bound to existing users (a verified whitelist). The columns are Email Address, User, User Email, Enrollment, Source and Actions; New email binding adds one.

warning
A binding proves that an address belongs to a user (enrollment Strong). A given inbound mail is trusted only as far as its DKIM/DMARC verdict: the SMTP From is spoofable. A message without a valid, aligned DKIM/DMARC pass resolves only as Weak and can never authorize an elevated operation, even from a whitelisted address.
Without bindings the list says "No records available.".