dovecot - Oct 2018 - Delete vs. Expunge in Public Namespace

All,

my IMAP client [1] marks messages as deleted, but doesn't expunge.
Dovecot (2.2.27-3+deb9u2) expunges them. Is this because the mailbox is
part of public namespace?

....
::1.38247-::1.00143: MALP6 STORE
48,49,50,51,52,53,54,55,56,57,58,59,60,61 +FLAGS (\Deleted)

::1.00143-::1.38247: * 48 FETCH (FLAGS (\Deleted \Seen))
* 49 FETCH (FLAGS (\Deleted \Seen))
* 50 FETCH (FLAGS (\Deleted \Seen))
* 51 FETCH (FLAGS (\Deleted \Seen))
* 52 FETCH (FLAGS (\Deleted \Seen))
* 53 FETCH (FLAGS (\Deleted \Seen))
* 54 FETCH (FLAGS (\Deleted \Seen))
* 55 FETCH (FLAGS (\Deleted \Seen))
* 56 FETCH (FLAGS (\Deleted \Seen))
* 57 FETCH (FLAGS (\Deleted \Seen))
* 58 FETCH (FLAGS (\Deleted \Seen))
* 59 FETCH (FLAGS (\Deleted \Seen))
* 60 FETCH (FLAGS (\Deleted \Seen))
* 61 FETCH (FLAGS (\Deleted \Seen))
MALP6 OK Store completed.

::1.38247-::1.00143: MALP7 SEARCH DELETED
....


Oct  2 10:18:03 hyptest dovecot: imap(chris): delete:
box=MailingListen/test125, uid=180,
msgid=<740a9ba3-d637-3fa0-1b87-ff8d79491bf0@ hyp.postbox.xyz>,
size=1509 Oct  2 10:18:03 hyptest dovecot: imap(chris): expunge:
box=MailingListen/test125, uid=167,
msgid=<740a9ba3-d637-3fa0-1b87-ff8d79491bf0 @hyp.postbox.xyz>, size=1509


namespace {
  list = yes
  location maildir:/var/vmail/public/:LAYOUT=fs:INDEXPVT=%h/.public-indexes
prefix
= MailingListen/ separator = /
  subscriptions = no
  type = public
}


- Chris






[1]
https://raw.githubusercontent.com/quentinsf/IMAPdedup/master/imapdedup.py

On Tue, 2 Oct 2018 18:04:21 +0200
Chris wrote:
> Is this because the mailbox is
> part of public namespace?
Or are they expunged because they're duplicates? Is there any check?
Based on Message ID?

- Chris

On 3 Oct 2018, at 9.03, Chris <chris2014 at postbox.xyz>
wrote:
> 
> On Tue, 2 Oct 2018 18:04:21 +0200
> Chris wrote:
> 
>> Is this because the mailbox is
>> part of public namespace?
> 
> Or are they expunged because they're duplicates? Is there any check?
> Based on Message ID?
No.. None of this makes sense. Dovecot doesn't auto-expunge \Deleted mails
in any situation.

I see your tool says:

    parser.add_option("",   "--no-close", 
dest='no_close', action="store_true",
                        help='Do not "close" mailbox when done.
Some servers will purge deleted messages on a close command.')

If it's sending CLOSE, that explains it. It's not just "some
servers", it's all IMAP servers. There's UNSELECT command to close
without expunging.