Hi
THis is the coredump detail on 2.3.17
Returning to 2.3.16 resolves the issue
(gdb) bt full #0 fts_user_autoindex_exclude (box=<optimized out>, box@entry=0x55cf79d865c8) at fts-user.c:347 fuser = <optimized out> #1 0x00007f1f31198496 in fts_mailbox_allocated (box=0x55cf79d865c8) at fts-storage.c:806 flist = <optimized out> v = 0x55cf79d865f0 fbox = 0x55cf79d86bf8 #2 0x00007f1f31825ccc in hook_mailbox_allocated (box=box@entry=0x55cf79d865c8) at mail-storage-hooks.c:256 _data_stack_cur_id = 5 _foreach_end = 0x55cf79d77088 _foreach_ptr = 0x55cf79d77078 hooks = 0x7f1f311c6ba0 <fts_mail_storage_hooks> ctx = 0x55cf79d87df8 #3 0x00007f1f31820ec1 in mailbox_alloc (list=0x55cf79d7dfd8, vname=0x7f1f318e439e "INBOX", flags=flags@entry=0) at mail-storage.c:885 _data_stack_cur_id = 4 new_list = 0x55cf79d7dfd8 storage = 0x55cf79d7e7e8 box = 0x55cf79d865c8 open_error = MAIL_ERROR_NONE errstr = 0x0 __func__ = "mailbox_alloc"