[EAI] The value of simplified downgrade

[Ernie Dainow <edainow at ca.afilias.info>]

There is a question of whether the EAI spec should include simplified 
downgrade at all. To help answer this, compare what a user has to do in 
various situations when there is downgrade and when there is not. From 
the user's point of view, there are not that many cases to consider.

1. Sending email to an EAI user ("sending" includes compose new mail, 
forward, reply).
This case will not have downgrade. If any recipients cannot in fact 
receive EAI mail, it will bounce. This is being considered a 
'configuration' error. Note this is different from the current Downgrade 
spec which supports downgrade to forward pointing addresses.

2. Sending email to an non-EAI user.
a. If EAI has downgrade, the user may use his EAI email account. As long 
as an alternate address has been configured, the mail will be downgraded 
using the supplied ASCII address as the From address.
b. If there is no downgrade, the user will have to use his non-EAI email 
account. This is slightly awkward, but not be a major hindrance. Many 
people are used to managing more than one email accounts, for example 
one for work and a second for personal email.

3. Sending email to a mix of EAI and non-EAI users.
a. If EAI has downgrade, the user may use his EAI email account and send 
a single message, freely mixing EAI and non-EAI addresses on To, Cc, etc.
b. If there is no downgrade, the user will have to send the same email 
twice; once using the EAI account for the EAI recipients and a second 
time using the non-EAI account for the non-EAI recipients.

Note that in 3b, EAI users and non-EAI recipients do not know the whole 
list of recipients, and Reply All will not reach the full list (unless 
the original sender is very disciplined and copies replies from EAI to 
non-EAI recipients and vice versa).

By comparison, in 3a, EAI recipients will see all the people that 
received the email and Reply All will reach everyone. However, non-EAI 
recipients will not see any of the EAI recipients, and their Reply All 
will only reach the non-EAI recipients and the sender. This is a 
consequence of dropping double angle brackets on forward pointing 
addresses, and was pointed out by Harald as the "triangle" case. As 
noted in that discussion, even with double angle brackets the triangle 
case will not consistently work in practice, as it depends on users 
being sufficiently disciplined to undertake the extra effort of entering 
alterrnate addresses for all EAI email addresses.

Clearly, the pain is case 3b. To the extent that we wish to improve on 
this scenario, we should include downgrade.

A second consideration is the effect on encouraging and speeding the 
migration to EAI from legacy email systems. Without downgrade, people 
have to actively maintain two email accounts. Under this circumstance, 
they may just choose the non-EAI account as the primary. With downgrade, 
there is an incentive to use the EAI account as the primary account, 
since it handles mail for all cases 1, 2 and 3.

One of the assumptions in a simplified downgrade is that it is not 
perfect (does not handle every possible case) and may lose some audit 
trail information. We need to decide if an imperfect downgrade is still 
better than no downgrade at all.

   -Ernie