Cannot deliver to shared folders with spaces - Kolab on Debian10

[teardrainer at web.de]

Hi all,

as the title says: We are running Kolab on a Debian10 system and have problems delivering mails to shared folders which have spaces in their names. This happens with existing and newly created shared folders. Our old system on CentOS never had a problem with this.

this works:
shared+shared/Customers/BigBlueCompany/Orders at ourdomain.com

this results in 550-Mailbox unknown:
shared+shared/Customers/Big Blue Company/Orders at ourdomain.com

The problem seems to be the local mail transport from postfix to cyrus via lmtp. I have compared the logs and the only difference I see is the quoting of the folder name when spaces are present. Taken from the lmtp transfer:

no spaces:
<sender at t-online.de> SIZE=4902
<shared+shared/Customers/BigBlueCompany/Orders at ourdomain.com>
 DATA
 250 2.1.0 ok
 250 2.1.5 ok
 354 go ahead

spaces:
<sender at t-online.de> SIZE=4912
<"shared+shared/Customers/Big Blue Company/Orders"@ourdomain.com>
 DATA
 Mailbox does not exist
 250 2.1.0 ok
 550-Mailbox unknown.  Either there is no mailbox associated with this
 550-name or you do not have authorization to see it.
 550 5.1.1 User unknown

AFAIK the quoting is expected behaviour and should work?

Could anybody running on Debian10 try to reproduce this?
If it's not an OS problem any hints on how to solve this would be appreciated.

Thank you

  Bob