Subject: [EAI] recap from IETF79 (Beijing) discussion on POPIMAP-Downgrade

From: Joseph Yee <[email-masked]>
Date: Tue, 26 Jul 2011 01:21:23 -0400

All,

Below is recap for WG discussion & consensus during IETF79 (Beijing) on interfacing between ASCII-only mail client with UTF8-capable POP/IMAP servers where mail stores hold UTF8-native messages.  

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The WG concluded that there is a need to relax RFC5322 to allow group syntax, with the intention that
i.    the message preserve the information that legacy mail client can display to end users
ii.   the message has higher chance be parse-able by legacy mail client so it's not lost
iii.  although the legacy client cannot reply back, there's no security concern of reply to wrong people

The goal is to make message readable for legacy client by RFC2047 (or by MIME Extension)

Various forms of presentation discussed, and agreed that group syntax works best for both issue 1 and issue 2 with the following details

Issue 1
Providing nested group (or even group with long list of addresses) is complex, and fragile (easy to break, not get parse properly as expected).  So the recommendation is create group only for the outermost group, any group within needed to be MIME encoded by RFC2047.

Issue 2
To use group syntax.  MIME encode the string (address) as group name, append :; to form an empty group list.

Additional changes to popimap-downgrade-display:

The draft popimap-downgrade UPDATES RFC5322.  This draft allows group syntax on backward pointing addresses (From, Resent-From, Sender, Resent-Sender) where RFC5322 prohibited.  RFC5322 intends to make sure message reply to a legit address, where EAI intends to display the message to end users, where users can take the internationalized string/address outside legacy mail client for further use, but not allowing the legacy client to reply.  Legacy client has no UTF8SMTPbis capability to reply.

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Regards,
Joseph