SCHEDULER/MTA: rework algorithm to have MTA request envelopes from SCHEDULER about opensmtpd

[poolpOrg]

being worked on currently !

[ericfaurot]

This can't be done like this directly, because the scheduler doesn't now about the
actual route for the envelopes.

[ericfaurot]

I want to close this ticket since I don't think it's worth doing it that way with the new mta design.
What we might do is have the mta send some kind of hints about the states of its routes, in case the
scheduler can use the info, but it should not be mandatory.

Or maybe file the ticket as "ideas for later".

[poolpOrg]

I would prefer that we keep it as an idea for later rather than closing.

With the other design we had optimal deliveries, with the current design I can observe we're much much much better than what we had but I don't know the details as I just read it from surface. I have no idea what we lost / won from the current design versus what we had discussed, I thought we were in a temporary state because the other design was too tricky to get at the moment.

[poolpOrg]

closing, we have done many improvements that makes this unnecessary