Lookup for "553 2.7.2"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (553)
Requested action not taken: mailbox name not allowed [E.g., mailbox syntax incorrect]
Enhanced Status Code Details (2.7.2)
Mailing list expansion prohibited
The sender is not authorized to send a message to the intended mailing list. This is useful only as a permanent error.