Canon VB-C300 Administrator's Manual page 284

Messages List
●
A List of SMTP Error Codes
Codes
421 <domain> Service not available, closing
transmission channel
450 Requested mail action not taken:
mailbox unavailable
451 Requested action aborted: local error in
processing
502 Command not implemented
550 Requested action not taken: mailbox
unavailable
284
Error Messages Description
The communication is terminated
because the mail server stopped.
The requested mail process was not
executed because the mailbox is not
available.
The requested execution was canceled
because an error occurred in the mail
server.
The mail server does not support the
command that was sent.
The request was not executed because
the mailbox is not available.