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Re: [sieve] New Version Notification for draft-george-sieve-vacation-time-00

2010-02-06 17:36:30

A propos the default sending address of vacation messages:

On 2/4/2010 4:58 AM, NED+mta-filters(_at_)mauve(_dot_)mrochek(_dot_)com wrote:
>> Dilyan says...
>>> State that replies are sent by default with "From" as the envelope
>>> recipient (when feasible) currently receiving the message.
>> No; this draft will make no incompatible changes to the base Vacation 
>> Unless, of course, the working group really wants to.
> First of all, since Sieves aren't always evaluated by SMTP servers prior to
> final delivery and may in fact be evaluated by MUAs after final delivery, the
> envelope recipient address may not be available for use in this way. As such,
> we cannot possibly impose such a requirement without also restricting the
> domain within which the extension can be used, probably to an unacceptable
> degree.

Vacation responses are sent if it is recognized that the current
recipient is mentioned in To/CC/Bcc/Resent-To/Resent-Cc/Resend-Bcc
headers.  This recognition matches the known addresses of the recipients
(mailbox name and everything mentioned in :addresses) towards the
To/CC.. headers.  If a match is found, then the vacation is sent...
using the found address in the From header.

Not necessarily. See the :addresses parameter. And before you say that messages
should be sent willy-nilly using the value of an addresses parameter, think for
a moment about things like sender-id and DKIM.

My idea was to send by default (vacation without :from parameter) the
vacations From the address of the recipient, not From the address of the
current mailbox.  Even if the SMTP envelope is not available at the time
the sieve script is evaluated, the engine can still figure out the
suggested From address, as indicated above.

Not true. See above.

> In cases where a Sieve owner has multiple addresses I understand the desire
> for the message to come from whatever address the originator used in order
> to lessen confusion, but the reality is that such a requirement cannot 
> be met.

Considering the above way of determining the From address, why cannot
the requirement

    Unless explicitly overridden with a :from parameter, the From field
    SHOULD be set to the address of the owner of the Sieve script.

be met?

Of course it can, and this is why the RFC is worded the way it is instead of
saying that the message should, in the absence of a :from parameter, be
sent from the address of whatever matched in To/CC/Bcc.

Again, I have no problem with the text being amended to say that it is best to
use the variant of the owner's address that matched in  To/CC/Bcc if possibe. I
would strongly object to saying that whatever address matched SHOULD be used.

Can the variable expansion be explicitly disabled in the :from parameter
of vacation?

I considered this when the RFC was written, but I think it is neither necessary
nor sufficient. There are cases like the selection of a subaddress value where
variables could be useful, and not having variables doesn't prevent one from
using this mechanism to forge mail. That's why the RFC leaves the question
of permission checks on :from up to the implementation.

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