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   notification - 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 separately. 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 BOFs.