Bernardi Giorgio wrote:
2.2.2. Incoming point
This point permits the exchange of PEC messages and
notifications between PEC providers. It is also the point
through which ordinary mail messages can be inserted within the
circuit of certified mail.
The exchange of messages between providers takes place through
SMTP-based transactions, as defined in [SMTP]. If SMTP
communication errors occur, they can be handled using the
standard error notification mechanisms, as provided by SMTP in
[SMTP] and [SMTP-DSN], however if the message is coming from
another PEC provider for the notification of the error the PEC
message for "Non-delivery notification" should be used in place of
the SMTP error.
When SMTP communication errors occur, the error notification is
generated by the sending PEC server itself, not the intended receiving
one -since the communication error would occur before the message
reached the destination. That notification is sent to the server's
service mailbox (not the user's mailbox), and after a certain amount of
time the Timeout Delivery Error Notification is generated by the sending
server.
The only case we can think of in which the receiving server could send
an SMTP error, would be if the MTA at the receiver's side got hold of
the message and ran its standard checks on it -therefore rejecting it-
rather than having PEC checks run on the message. This though must not
happen, since all messages have to be accepted by the PEC server.
A minor adjustment though will be the following:
"If SMTP communication errors occur, they MAY be handled using the
standard error notification mechanisms, as provided by SMTP in
[SMTP] and [SMTP-DSN]."
--Alba