Re: Mailing lists as 2822-Sender (was: Responsibility vs. Validity)

Dave Crocker wrote:
> 
> 
> Tony Finch wrote:
>>>      "The "Sender:" field specifies the
>>>    mailbox of the agent responsible for the actual transmission of the
>>>    message."
>>
>> Popular MTA implementations (Sendmail, Postfix) do not implement the
>> Sender: header the way 822 and 2822 suggest,
> 
> How would you describe what they do do?

Well, if SendMail/PostFix is operating like the rest of the world... If 
missing, a SMTP receiver MIGHT do:

    Sender: <-- x821.MailFrom

in the same vain many SMTP receivers will fill in the missing 822 
required fields.

    FROM:  <<-- x821.MailFrom
    To:    <<-- x821.RcptTo

and they MUST do this if they want to SUPPORT the presentation layers.

But sender is not a given because it is not a 822 required field. In 
fact, I seem to recall, it was only in recent years that we even 
bothered with Sender in our mailers.

Only a few sites will reject such empty headers in the DATA block. Off 
hand, I know of one, HOTMAIL.COM and they only started to reject mail 
without the headers when SENDER-ID support was added to HOTMAIL.COM.

-- 
Sincerely

Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com