RE: [draft-ietf-opes-smtp-use-cases-01]

On Sat, 22 Jan 2005, Martin Stecher wrote:
>
> I do not want to reject a reasonable respmod scenario, I just do not
> understand why this IS a response modification example.
>
> Tony describes how it is being solved today by using abbreviated
> SMTP comunication. This can be translated into request satisfaction
> in OPES as I described.

I brought it up because I think it's worth thinking about, if only to
conclude that the proposed model is the right one.

The reason I thought it could perhaps be considered as a response
modification scenario is that the destination server's 4xx response is
converted by the MX server into a 2xx response. In addition to that it's
rather ugly to have the OPES callout server implement the SMTP
call-forward, because you have to duplicate knowledge of email address
routing in the MTA and the OPES callout server. Yes, you can fix this
problem by using better ways of distributing knowledge about shared
addresses, but this requires co-operation between the people that run the
two MTAs and this may not be practically feasible. (In the case of
Cambridge the University is run on a rather federal basis, so the
Computing Service can't impose technical requirements on departments.
Another situation in which this technique is useful is when a site has
secondary MXs run by a different organization.)

However as you say it doesn't really fit into the OPES model because the
call-forward is not a full SMTP conversation (it's a hack), so it's
probably too much of a strain to support something that's fairly esoteric.

Tony.
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