[MlMt] really delete

[Bill Cole]

On 27 Oct 2016, at 8:02, Randy Bush wrote:

>> Right clicking on the 'Deleted Messages' folder in the left
>> hand pane will present a contextual menu.  Select
>>    Empty "Deleted Messages"
>
> aha!  that's it.  my use pattern is
>     o i do not display MAILBOXES, only SOURCES
>     o i am  not subscribed to Deleted Messages, do you subscribe
> 	to your rubbish bin? :)

This is a use pattern encouraged by IMAP, although clients actually vary 
substantially in how they implement it. Total message deletion is never 
an atomic operation in IMAP, there is always an intermediate state 
whereby a message is poised for deletion but can be recovered.

If the IMAP server supports the MOVE extension, MM uses it to move a 
message (o set of messages) into whatever IMAP mailbox is the logical 
"Deleted Messages" mailbox for that account and expunges the message 
from the original mailbox all in one step. If the IMAP server does not 
support MOVE, it uses a non-atomic mechanism: copy the message to 
Deleted Messages, mark the original with the "\Deleted" flag, and 
expunge it. If you do not subscribe to the IMAP mailbox that MM has 
marked as the logical "Deleted Messages" mailbox for the account, it 
will accumulate messages indefinitely, never REALLY removing them.

Another way that some clients implement a logical "Deleted Messages" 
mailbox which doesn't really exist on the IMAP server is to keep track 
of what messages have the "\Deleted" flag and hide them from view in the 
IMAP mailbox where they really are. This model is popular with older and 
especially "offline mode" clients that maintain an independent local 
message store which is synchronized intermittently and does not 
perfectly represent server state. This is probably because the MOVE 
operation was not a standardized part of IMAP until 2013, making the 
non-atomic nature of logical message moves a source of difficulties.

The model of having a server-side trashcan is better fit for the modern 
reality of multiple disparate clients

> so i was not seeing this path at all.
>
> thanks!

If emptying the trash in MM is actually a solution, it implies that 
there's something wrong with either your IMAP server or the other 
client. The fact that you refer to wanderlust having "it's equivalent of 
inbox" makes me suspect that it does not expect another IMAP client to 
be active and doing what MM does and/or that it simply isn't 
resynchronizing frequently enough to notice vanishing messages.