> That's a point I can understand. If Sieve focuses only on messages,
> then manipulating persistent folder attributes would be simply out of
> scope. Does it focus strictly on messages, not folders, despite
> folders containing messages?
Yes. Sieve ignores folders almost entirely. (Except that fileinto may
create a folder.)
And IMAP's folder-level capabilities are somewhat limited.
> If so, how about message attributes to allow expiration to happen?
Much better.
Such attributes are called annotations in IMAPspeak, and they're
supported by the ANNOTATE extension, which is itself still a draft and
not terribly widely implemented. If there isn't yet a sieve extension
to set a message annotation, there certainly should be.
Yes, a sieve extension to interface with the IMAP ANNOTATE extension makes
sense, assuming of course that IMAP ANNOTATE is approved. But it only makes
sense to use annotations for storying expiry information if it is done
per-message. And even then a separate IMAP extension would need to be defined.
Ned