[Evolution-hackers] The Junk problem and IMAP

[Not Zed <notzed ximian com>]

Ok, there's a lot of problems with this:

 - first, its just F***n slow, but there's nothing that can be done
about that
 - second, it filters all folders.  We rely on the server to tell us
when we have new mail ('Recent'), but we get Recent whenever we copy
from local to imap, between imap servers, and possibly between folders
on the same imap server (the imap spec doesn't specify this).  i.e. as
soon as you move messages around, it re-filters.  Yucko.

So I tried:
 - adding a couple of new flags, Junk and NotJunk

   So that once we've done junk processing, we dont need to do it again
   We can set the flags on most servers (but not all) when we append
messages, and the server should keep the flags when we copy between
servers.

  Except, at least for uwimapd, it wont let you set custom flags during
an APPEND, even when it is part of the PERMANENTFLAGS response.  Fun eh.

The other alternative
 - use UIDPLUS to find out what the newly appended UID is, and STORE the
flags manually

  Drawback is even fewer servers support UIDPLUS than custom flags, so
its kind of pointless.

The only other possibility
 - assume the server will copy the flags with COPY (probably not
entirely safe to assume)
 - when we do APPEND, set a specific one-off header in the message to
say its been junk filtered/the junk filter result.

But, the later could lead to inconsistencies if we later change the junk
state, and it just doesn't seem very clean anyway.

I propose we ONLY do junk processing on INBOX, as we do with other
filters.  At least that gets around most of the issues without more
nasty server-specific (or worse) hacks.  Or well, we do it in a totally
different way (but we'll still have the issue of re-junk testing
everything anyway, so it wont fix anything).

If people are already doing server-side filtering, they really should be
doing server-side junk filtering too ... (well, i did suggest we had
per-server junk settings so we could deal with this somehow in the ui,
but ...).

 Z