dovecot - Sep 2017 - Mac Os mail error while moving msg in subfolder

Hi all

we are experiencing several errors like this:

WROTE Sep 05 11:30:57.700 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
35.156 UID COPY 76543 GARR.Eduroam_tech

READ Sep 05 11:30:57.702 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
35.156 NO [CANNOT] Character not allowed in mailbox name: '.' (0.001 +
0.000 secs).

WROTE Sep 05 11:30:57.719 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
36.156 UID STORE 76543 +FLAGS.SILENT (\Deleted)

READ Sep 05 11:30:57.733 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
* 7776 FETCH (UID 76543 MODSEQ (201448))
36.156 OK Store completed (0.012 + 0.000 + 0.011 secs).

WROTE Sep 05 11:30:57.734 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
37.156 IDLE

READ Sep 05 11:30:57.740 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x60000127b140
+ idling

READ Sep 05 11:31:08.857 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6000004b1dc0 --
thread:0x608001475180
* OK Still here

READ Sep 05 11:31:09.369 [kCFStreamSocketSecurityLevelTLSv1_2] --
host:mail.uniparthenope.it -- port:993 -- socket:0x6080006ba580 --
thread:0x608001475180
* OK Still here

while a mail client on mac os tries to move a message to a subfolder

Dovecot version in use is: 2.2.31

and the configuration extract file is:

namespace {
   disabled = no
   hidden = no
   ignore_on_failure = no
   inbox = yes
   list = yes
   location    order = 0
   prefix    separator = /
   subscriptions = yes
   type = private
}
namespace {
   disabled = no
   hidden = yes
   ignore_on_failure = no
   inbox = no
   list = no
   location = maildir:~/Maildir/expunged
   order = 0
   prefix = .EXPUNGED/
   separator = /
   subscriptions = yes
   type = private
}

all other client like thunderbird, outlook and horde imap web interface 
work fine.

Is there something who could help me?

thank you

regards

-- 
Dott. Antonello Cioffi
Ufficio Servizi Informatici
Universit? degli Studi di Napoli Parthenope
Tel. 081/5475292 - Fax. 081/5475180