Message Not Delivered: Mailbox has a mailing list system issue
The message could not be delivered because the recipient's email address, which is a mailing list, had trouble forwarding the email message the list members.
Check that the recipient's email address is the correct address for the mailing list you wish to reach. If an error is found, correct it in contacts list or address book for next time.
Contact the administrator of the mailing list for help.
5.2.4: Official Definition
A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery.
The mailbox is a mailing list address and the mailing list was unable to be expanded. This code may represent a permanent failure or a persistent transient failure.