[Dovecot] Move deleted to trash

[Donald Nash]

--On July 25, 2007 4:55:06 PM +0300 Timo Sirainen <tss at iki.fi> wrote:

> EXPUNGE command is specified to expunge the mails, not move them to
> another mailbox. This would make having the message really gone a 4 stage
> operation: Mark deleted, expunge, mark deleted in Trash, expunge Trash.

This same complaint can be lodged against lazy-expunge.  The cure, of 
course, is for the server to keep such folders (whether they are trash 
folders or the more complicated hierarchies that lazy-expunge creates), 
cleaned up by expunging messages older than a certain age.  You're working 
on that with the Expire plugin.  Other IMAP servers I've seen which 
implement a server-managed trash folder do this specifically for the trash 
folder.  In either case, it means you can continue to use the the "mark 
deleted, then expunge" model, and not worry that the messages are really 
just being moved somewhere else temporarily.

> In many clients when you mark a message deleted it also copies it to
> Trash. So a server side expunge-to-trash feature causes the message to
> get copied there twice.

So turn it off in one place or the other.  Every mail program I've looked 
at that implements a client-managed trash folder located on the IMAP server 
has a configuration setting for turning it off.  Or you can turn it off on 
the server if you'd prefer that clients do it for themselves.

> A Trash mailbox also has the problem that all of your messages get there.
> There's no way to have an easy "unexpunge" operation, because the
> original mailbox isn't saved anywhere. You have to manually copy the
> message to the wanted mailbox.

This seems like a moot point to me.  A proper unexpunge operation cannot 
exist until either it is added to the IMAP standard, or something like 
lazy-expunge gets enough traction for the authors of IMAP clients to start 
writing code to use it (have any done so?).  Until then, restoring deleted 
messages directly from the IMAP client will always involve having the user 
find the proper folder and copy the message elsewhere.  This is exactly 
what he'd have to do to retrieve the message from a trash folder, except it 
is somewhat more complicated because of the need to find the right folder 
containing the expunged message.

As mentioned in the documentation for lazy-expunge, you could have a web 
interface to handle unexpunging.  While this would be useful for restoring 
large groups of messages or entire deleted folders, it is still something 
of a hack because it is done "behind the back" of the IMAP client.  I'm not 
saying it isn't worth doing, just that I wouldn't call it a *proper* 
unexpunge operation (I'm defining "proper" as meaning "available directly 
from an IMAP client", others may have different definitions).  It also 
isn't supplied with Dovecot, so it would either need to be written from 
scratch or obtained from someone else who has already written it.

> Perhaps lazy-expunge is a bit similar, but it preserves the mailboxes and
> doesn't conflict with clients' move-to-Trash feature. Also the concept in
> general is about having easily restorable backups of mails and not some
> kind of a idea that mails should go to a Trash mailbox when they're
> deleted.

Both features are fundamentally about the same thing: being able to recover 
messages which should not have been deleted.  Also, they both involve 
taking messages which are being expunged and copying them to another folder 
prior to expunging them (thus arguably violating the strict definition of 
"expunge").  The only technical difference is the folder to which they get 
copied.  That technical difference makes for a big functionality 
difference, and lazy-expunge is therefore a more comprehensive solution. 
But this comes at the expense of being a bit harder to use in the trivial 
cases.

> The virtual Trash would make client-side "delete=mark deleted + copy to
> Trash" feature unnecessary.

Except that's not how client-side trash folders work, at least not the ones 
I've seen.  They don't move a message into the trash folder until you 
expunge it, not when you mark it for deletion.

> Well, I Cc'd the list now.

And since this has turned into much more of a discussion than I 
anticipated, I've done what I should have done in the first place and 
joined the list.

-- 
Donald L. Nash, <D.Nash at its.utexas.edu>
Information Technology Services, The University of Texas at Austin