Re: Last Call: SMTP Service Extension for Content Negotiation to Proposed Standard

> IMO, the ultimate aim (even if this is not practical) is to deliver
> to each recipient the same version of the Fax as they would have
> received IF they were the only addressee 

I think this is a reasonable and practical goal.  I don't think that 
recipient A should experience a difference in message quality 
(or worse, fail to receive the message at all) based on whether or 
not you cc'ed recipient B.

> while at the same time
> generating only the minimum number of copies to allow
> multi-addressing.

I think this is an implementation decision.  It should be *possible*
to do this (and it is), but it shouldn't be required of implementations.


here are a couple of trivial examples of the effect of a "downgrade to 
LCD format" implementation strategy.  

assume:

recipient A accepts only HTML and plain text
recipient B accepts only PDF and plain text

an HTML message sent only to A gets delivered as HTML, but if B is cc'ed 
(or bcc'ed) on the message then both A and B get plain text (if the 
client knows how to convert HTML to plain text).  A is accustomed
to receiving HTML from B and is surprised that there's an information
loss.

more seriously, a PDF message sent only to B gets delivered as PDF, but 
if A is cc'ed on the message then the message is bounced for both A and 
B because there's no good way to downgrade PDF to a format acceptable 
to B (or the client doesn't know how).  

So far I have not been able to identify conditions for which downgrading 
to LCD is a viable implementation strategy.  My conclusion is that
implementations that support CONNEG and that attempt to deliver to
mutliple recipients in one transaction MUST be prepared to do RSET and 
split up the delivery if it becomes evident that delivering the same 
version of the message to all recipients is not appropriate.

Keith