Hello (Timo),

depending on the client (with OfflineIMAP, but not a mobile one) my dovecot test configuration (config on request) crashes if mailbox_list_index=yes:

Apr 9 09:26:31 host dovecot: imap-login: Login: user=<user>, method=CRAM-MD5, rip=2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, lip=2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, mpid=19028, TLS, session= Apr 9 09:26:31 host dovecot: imap(19028, user) /+vqeOjZ1wAgAQY4BgPRMwIMKf/+amcv: Panic: file mail-index-view.c: line 169 (view_lookup_full): assertion failed: (seq > 0 && seq <= mail_index_view_get_messages_count(view)) Apr 9 09:26:31 host dovecot: imap(19028, lpmailext) /+vqeOjZ1wAgAQY4BgPRMwIMKf/+amcv: Error: Raw backtrace: /usr/lib/dovecot/libdovecot.so.0(+0x61 75a) [0x7fca0248c75a] -> /usr/lib/dovecot/libdovecot.so.0(+0x617a6) [0x7fca0248c7a6] -> /usr/lib/dovecot/libdovecot.so.0(i_error+0) [0x7fca0244d3cf] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0xc9b5e) [0x7fca027adb5e] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0xca238) [0x7fca027ae238] -> /usr/lib/dovecot/libdovecot-storage.so.0(mail_index_lookup_ext+0x17) [0x7fca027ad2b7] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_index_status+0x11f) [0x7fca0277559f] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_index_status_set_info_flags+0x8d) [0x7fca0277606d] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_index_iter_next+0x18d) [0x7fca0277383d] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x93177) [0x7fca02777177] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_iter_next+0x255) [0x7fca02777465] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x94881) [0x7fca02778881] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x93177) [0x7fca02777177] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_iter_next+0x3c0)[0x7fca027775d0] -> /usr/lib/dovecot/modules/lib20_virtual_plugin.so(virtual_config_read+0x97d) [0x7fca0065344d] -> /usr/lib/dovecot/modules/lib20_virtual_plugin.so(+0x93c5) [0x7fca006553c5] -> /usr/lib/dovecot/modules/lib20_zlib_plugin.so(+0x2a8c) [0x7fca00447a8c] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x7dd94) [0x7fca02761d94] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_open+0xf) [0x7fca02761f4f] -> /usr/lib/dovecot/libdovecot-storage.so.0(index_mailbox_get_metadata+0x5da) [0x7fca0278a41a] -> /usr/lib/dovecot/modules/lib20_virtual_plugin.so(+0x8d48) [0x7fca00654d48] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x91f05) [0x7fca02775f05] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_get_metadata+0x6e) [0x7fca02761b6e] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_list_index_sync_name+0x2e6) [0x7fca02776b66] Apr 9 09:26:31 host dovecot: imap(19028, user) /+vqeOjZ1wAgAQY4BgPRMwIMKf/+amcv: Fatal: master: service(imap): child 19028 killed with signal 6 (core dumped)

gdb bt full attached. Haven't tested yet if disabling virtual namespaces makes a difference. Neither logged triggering IMAP commands.

Regards, Lutz