[MASOCH-L] Mail From Vazio

[Andre Ramoni]

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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