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