[RFCI-Discuss] multi-MAIL commands appearing in the same mail-transaction?

[Derek J. Balling]

On Jun 6, 2006, at 8:34 AM, Jeff Pang wrote:
> Hello,I saw them in RFC2821 below:
>
>       The first step in the procedure is the MAIL command.  The
>         <reverse-path> contains the source mailbox.
>
>            MAIL <SP> FROM:<reverse-path> <CRLF>
>
>         This command tells the SMTP-receiver that a new mail
>         transaction is starting and to reset all its state tables and
>         buffers, including any recipients or mail data.  It gives the
>         reverse-path which can be used to report errors.  If accepted,
>         the receiver-SMTP returns a 250 OK reply.
>
>         The <reverse-path> can contain more than just a mailbox.  The
>         <reverse-path> is a reverse source routing list of hosts and
>         source mailbox.  The first host in the <reverse-path>  
> should be
>         the host sending this command.
>
>
> It say 'The <reverse-path> can contain more than just a mailbox'.As  
> I think,each mailbox mean a MAIL FROM command,so there would permit  
> multi-MAIL commands.Is it right?

No, I would interpret that as something like, it could have  
+notation, or other arguments, stuff like that. Not that multiple  
MAIL commands are valid.

> helo 163.com
> mail from:<abcd at 163.com>
> mail from:<efgh at 163.com>
> rcpt to:<xxxx at gmail.com>
> data
> quit

>
> When I open my gmail and see that message's original header,I got:

> Return-Path: <efgh at 163.com>
> It seems that the second MAIL FROM has overcovered the first MAIL  
> FROM.
> It's somewhat confused for me,I think.

GMail's implementation is following a literal interpretation of  
RFC2821. The second MAIL command is "a new mail transaction" and thus  
it "resets all its state tables and buffers", so essentially the  
first MAIL command is completely gone, its state erased.

Cheers,
D


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