From the I-D "Email Submission Between Independent Networks",
which hopes to be a BCP:
(<http://www.ietf.org/internet-drafts/draft-hutzler-spamops-00.txt>)
"Similarly, an MDA can choose
to reject all mail to recipients for which that MDA has no
arrangement to perform delivery."
Indeed, this is best practice; it should be added to the
"Best practices are:" section, i.e. suggested text:
o MDAs SHALL NOT accept mail to recipients for which that MDA
has no arrangement to perform delivery.
Comments?
From the I-D:
"Comments and discussion of this
document should be addressed to the ietf-smtp(_at_)imc(_dot_)org mailing
list."
Also emailing the ASRG, as participants from the ASRG are referenced in the I-D
as a source of input.
Apologies, as this is likely not terribly timely.