Re: Email System Model

David MacQuigg wrote:
> Alessandro Vesely wrote:
> > I had hoped that a protocol for configuring forwarding would have 
> > smoothly lent itself to also configure secondary MXes
> The model at http://open-mail.org/MHSmodels.html is an 
> administrative-level model, not a relay-level model.   We are modeling 
> Actors (Users and Agents) and their roles in an email system.  Backup 
> MXs are relays under the control of the Receiving Agent, even if they 
> are actually subcontracted to a hosting service in another city.
It only makes sense to reserve a place for backup MXes in a model if 
such modeling is aimed at bettering the mail system, rather than 
merely describing how it currently does [not] work.
> To add a Backup Agent to the model, I would need to see an example of 
> how this might make a difference to any Actor interacting with the 
> Receiving Agent.   Yes, there are many problems with backup MXs not 
> having current information on a sender's greylist status, not knowing 
> when the primary MX is back in operation, etc., but how is that 
> different than a Receiver Agent that simply fumbles its internal 
> operations?
Externally administered backup MXes run into backscattering because 
they don't maintain a copy of the users database. To amend that status 
of affairs implies that a user's email address will also be stored at 
an externally controlled backup MX. Such situation should interest the 
users, as those addresses are part of their personally identifiable 
information. I say /should/ because the same is true for forwarding. 
In both cases, Actors should provide means for exercising their users' 
rights.