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Mail Recipient Capabilities

Document Charter Mail Recipient Capabilities WG (mailcap)
Title Mail Recipient Capabilities
Last updated 2011-12-09
State Approved
WG State Concluded
IESG Responsible AD (None)
Charter edit AD (None)
Send notices to (None)


There are a number of instances where it would be very useful
for a sender to be able to determine capabilities, or attributes,
of recipient's email address.  For example:

  • a sender of email might want to know whether the recipient
      is willing to accept HTML files

  • a sender of Internet fax (which runs over email) might like to
      know whether a recipient can handle color faxes, or high resolution

  • a sender of Internet fax might like to know whether the recipient
      will acknowledge receipt of the fax using a message disposition

  • a sender of email might want to know the recipient's public key(s)
      for encryption and/or signatures

  • a sender of email might want to know a the URL of a recipient's
      home page

It's also possible that a email recipient might want to know where to
find various services related to his email address, or other attributes
about those services, without having to configure each of them

A variety of mechanisms, some more satisfactory than others, have
been proposed to address one or more of these problems: including
using DNS by itself (perhaps with NAPTR or SRV records), DNS+LDAP,
DNS+ACAP, adding "recipient query" functionality to SMTP, and adding
attributes to message disposition notifications (MDNs) to allow
them to return recipient capabilities in email.

This BOF will attempt to determine the sense of the community
as to whether there should be a standard convention for mapping
an email address onto a set of attributes, perhaps outline
some of the requirements for such a convention, and to suggest
possible solutions.  If there is interest in establishing such a
convention, the BOF will also attempt to determine whether this
should be pursued as a working group or by some other means.

This BOF is being held back-to-back to the E.164 mapping BOF,
which is examining a similar problem - whether there should be
a standard convention for mapping E.164 numbers (i.e. phone
numbers) onto attributes of those numbers.  Since some services
(notably internet fax and voice mail) might use either Internet
email addresses or E.164 numbers to identify recipients, it
seems worth considering whether the two mapping services should
share common components.  And yet the two services are likely
to be used by different communities with possibly divergent views of
the requirements, which is why they're being discussed in separate