Sieve script unable to file into public folder after dovecot upgrade to version 2.3.4

[Andreas Oster]

Hi all,

Wishing you and your families a Happy New Year 2019.


I am currently struggling with an odd sieve issue after upgrading dovecot from 2.2.32 to the latest 2.3.4 version. OS is Ubuntu 18.04.
For one of our users I have a sieve rule in place which should copy (keep + fileinto) incoming mails from the INBOX to a public namespace folder.
Unfortunately this does not work anymore. In the sieve log file of the user I get error messages like this:

sieve: info: started log at Jan 02 12:41:31.
error: msgid=<dc6bdcb2-7efb-0f0a-3a6d-c1133233c11f at novanetwork.de>: failed to store into mailbox 'Public/Verteiler': Permission denied.  

This is the content of the sieve script :

require ["fileinto"];

keep;
fileinto "Public/Verteiler";
stop;


At first I thought it might be caused by a faulty IMAP ACL but this does not seem to be the case. When I do a manual copy in Thunderbird from the INBOX to this public folder there are no problems at all.

Does anybody have an idea what could be the cause of the issue ?

Thank you very much for your kind help.

Best regards
Andreas