Hi Aki,
Thanks for your prompt reply! :-) And because i classically forgot to attach the dovecot-sysreport, i'll deliver it now. :-)
Yes, you're right. Setting :LAYOUT=fs would be a workaround. I'd also have to migrate every single mailbox to the new hierarchical layout. The hierarchical separator list->sep would indeed change to „/‟ and the subscriptions would be split differently.
Please correct me when i'm wrong, but the namespace/separator would have to be changed too, to prevent splitting on another "wrong" position. The current shared/root@example com/test subtest would become to shared root@example.com test subtest. Which is also wrong because there is no user shared. So the namespace separator could be set to again something different (from „auth_username_chars‟ + "/+") like „^°!§%&=?;:#¹²³‟ which all would be ugly. And with namespace/sep set to „°‟ leading to the form shared°root@example.com°test subtest.
But this would not resolve the actual bug, that subscriptions are not split and persisted correctly. In the end i would just be forced to use :LAYOUT=fs to mitigate the bug, even if i like the flat layout. :-)
I think there should be a default, which is valid for a common deployment with all features working. Maildir++ for sure is a great choice for this, but the implementation has a flaw: a hard-coded „separator‟, which collides with the DNS label delimiter, when storing subscriptions.
Best Regards Tobias