Last Call Review of draft-ietf-extra-sieve-special-use-04
review-ietf-extra-sieve-special-use-04-secdir-lc-farrell-2018-12-17-00

As stated in the draft I see no new security issues here, given that SIEVE
already includes the ability to deliver messages and create mailboxes.

A non-security comment, that you should feel free to ignore: as a mail user it
is irritating to have multiple folders (that may or may  not have a 
"special-use" attribute associated with 'em) created by multiple MUAs and into
which messages can be deposited in a manner that's unpredictable to me as a
user . I understand that this spec is already trying to help with that, by
reducing the likelihood that such redundant folders get created. But I already
have a bunch of those folders, so while this is likely the wrong place for such
text, I'd have been happier if the guidance for what to do when there's >1
matching special-use mailbox had been more deterministic, even when the
SIEVE-supplied default one doesn't exist. For example, if you'd been able to
say to sort the matching folders in some way and then pick the first that'd be
better I think, but maybe there are reasons why you can't do that in SIEVE.
(I'd be even happier if someone was working on specs/tooling to help merge all
those folders somehow, but that's definitely out of scope here.)