Re: [Emailcore] Ticket #15: G.7.9. Discussion of 'blind' copies and RCPT

[Alessandro Vesely <[e-mail]>]

On Tue 19/Jan/2021 17:11:45 +0100 Alexey Melnikov wrote:
> Dear collegues,
> 
> The 1st pagaraph of Section 7.2 ("Blind" Copies) currently says:
> 
>    Addresses that do not appear in the message header section may appear
>    in the RCPT commands to an SMTP server for a number of reasons. The
>    two most common involve the use of a mailing address as a "list
>    exploder" (a single address that resolves into multiple addresses)
>    and the appearance of "blind copies". Especially when more than one
>    RCPT command is present, and in order to avoid defeating some of the
>    purpose of these mechanisms, SMTP clients and servers SHOULD NOT copy
>    the full set of RCPT command arguments into the header section,
>    either as part of trace header fields or as informational or private-
>    extension header fields.
> 
> Suggested replacement for the last sentence quoted above (as per feedback from 
> Arnt Gulbrandsen):
> 
>    When more than one
>    RCPT command is present, and in order to avoid defeating some of the
>    purpose of these mechanisms, SMTP clients and servers SHOULD NOT copy
>    any of RCPT command arguments into the header section,
>    either as part of trace header fields or as informational or private-
>    extension header fields.
> 
> (This removes "especially" and replaces "the full set of" with "any" -- copying 
> the first one can be as harmful as copying all of them, at least without 
> verifying that the addresses do appear in the headers.)
> 
> Please provide feedback on this proposal within 2 weeks.


Having removed "especially", we could raise to MUST NOT.  Were there other 
circumstances that would allow violating the SHOULD NOT?

Anyway, this Section deserves a comefrom Section 4.4.  That is, for example:

    For            = CFWS "FOR" FWS ( Path / Mailbox )
                   ; Not if multiple recipients, see Section 7.2


Best
Ale
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