[Emailcore] Ticket #8: Need a registry of header fields that are Ok to add after submission

[Alexey Melnikov <[e-mail]>]

Dear WG participants,

Based on an earlier discussion on the mailing it looks like there is 
consensus to create (or possible ammend an existing) registry for header 
fields with extra information about which types of SMTP agents are 
allowed to add them in transit or before final delivery. In order to 
stimulate the discussion, I would like to propose the following strawman:

Add to IANA Considerations:

IANA is requested to create a new subregistry for email header fields 
that can be added to a message header section by a “relay” and/or 
“delivery” SMTP system. The new subregistry would show whether a header 
field can be added by a “relay”, “delivery” system or both. It will also 
include information whether the header field is allowed to be added 
multiple times or just once. Only header fields that are already 
registered in 
<https://www.iana.org/assignments/message-headers/message-headers.xhtml> 
(whether it is registered as a Permanent Message Header Field Name or as 
a Provisional Message Header Field Name) can appear in this new 
subregistry. Registration policy for this new subregistry is “Expert 
Review”.

Notes:

a) the reason why I am suggesting to create a new subregistry is because 
I think this will be far less work. The same registry is currently also 
used by HTTP and NNTP, so adding extra columns to convey the above 
information would likely confuse HTTP users of the registry. It would 
also be easier to do this if there is no need to get buy in from other 
users of the registry.

b) I believe John asked whether this should be "First Come First Served" 
or "Expert Review". I proposed to do the latter to make sure that 
somebody checks that a particular header field is indeeded added during 
relay/final delivery/both. The review process can be lightweight.

Comments please.

Best Regards,

Alexey