[MASOCH-L] Mail From Vazio
Andre Ramoni
andre.ramoni at gmail.com
Thu Feb 3 11:50:15 -03 2011
On Feb 3, 2011, at 11:34 AM, Leandro Carlos Rodrigues wrote:
>>> / Alguém sabe me explicar porque alguns MTA's não preenchem o comando MAIL
> />>/ TO: numa conexão SMTP para algumas mensagens?
> />
>> Nao seria os emails de/para o MAILER-DAEMON?
>
> Creio que seja isto. Mas aonde eu quero chegar é: porque não preenchem o campo com um endereço válido mesmo que seja o endereço do MAILER-DAEMON? Por que deixar o campo vazio?
>
Leandro, tem um motivo pra isso que é evitar loop em caso de msgs de erro conforme previsto na rfc 2821:
(...)
If an SMTP server has accepted the task of relaying the mail and
later finds that the destination is incorrect or that the mail cannot
be delivered for some other reason, then it MUST construct an
"undeliverable mail" notification message and send it to the
originator of the undeliverable mail (as indicated by the reverse-
path). Formats specified for non-delivery reports by other standards
(see, for example, [24, 25]) SHOULD be used if possible.
This notification message must be from the SMTP server at the relay
host or the host that first determines that delivery cannot be
accomplished. Of course, SMTP servers MUST NOT send notification
messages about problems transporting notification messages. One way
to prevent loops in error reporting is to specify a null reverse-path
in the MAIL command of a notification message. When such a message
is transmitted the reverse-path MUST be set to null (see section
4.5.5 for additional discussion). A MAIL command with a null
reverse-path appears as follows:
MAIL FROM:<>
As discussed in section 2.4.1, a relay SMTP has no need to inspect or
act upon the headers or body of the message data and MUST NOT do so
except to add its own "Received:" header (section 4.4) and,
optionally, to attempt to detect looping in the mail system (see
section 6.2).
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