Re: [Dovecot] unwanted maildir directory

So are you saying that this directory was actually created by Dovecot?

Yes. No migration, no Courier.

Are these easy to reproduce?

Yes, on my system. I'll try imaptest.

user1 is accessing user2's INBOX?

Not intentionally. User1 and user2 happen to be logged in at the same time and were assigned to the same imap process, that's all. They know nothing about each other and there are no namespaces or public folders or any of that.

Does one of these asserts catch it?

imap(pid 72709 user specmail773): Panic: file maildir-save.c: line 79 (maildir_file_move): assertion failed: (*mf->tmp_name != '\0') imap(pid 72770 user specmail52): Panic: file maildir-save.c: line 79 (maildir_file_move): assertion failed: (*mf->tmp_name != '\0')