Keith ``Interoperability? What's that?'' Moore writes:
no, I'll be suggesting that they throw away mail that grossly violates
the standards because trying to support too much garbage adds complexity to
the mail system and in the long run decreases its reliability.
According to that logic, I should change qmail to reject IDNA addresses.
Let's look at the facts:
* IDNA addresses grossly violate the full standards, which specify
that addresses are 7-bit ASCII. IDNA is 7-bit but not ASCII.
* This IDNA garbage adds a huge amount of unnecessary complexity to
the mail system. UTF-8 achieves the same goal at much lower cost.
* IDNA, in both the short run and the long run, decreases the
reliability of the mail system; IDNA causes many failures that
don't occur with ASCII addresses.
Meanwhile, I certainly don't have any legitimate IDNA mail in any of my
mailboxes; and I'm sure that blocking IDNA will stop some spam.
---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago