Mar 14 23:14:58 *** dovecot: service=imap, user=***, ip=[::1]. Panic: file mail-storage.c: line 1913 (mailbox_get_open_status): assertion failed: (box->opened)
Mar 14 23:14:58 *** dovecot: service=imap, user=***, ip=[::1]. Error: Raw backtrace: /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(+0xba731) [0x7f553a7ff731] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(+0xba7fa) [0x7f553a7ff7fa] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(i_fatal+0) [0x7f553a771638] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot-storage.so.0(mailbox_get_open_status+0x68) [0x7f553aae4a78] -> /usr/lib/dovecot/modules/lib21_fts_squat_plugin.so(+0x3684) [0x7f553677a684] -> /usr/lib/dovecot/modules/lib21_fts_squat_plugin.so(+0x3820) [0x7f553677a820] -> /usr/lib/dovecot/modules/lib20_fts_plugin.so(fts_backend_lookup_multi+0x163) [0x7f5539b016a3] -> /usr/lib/dovecot/modules/lib20_fts_plugin.so(+0xd728) [0x7f5539b06728] -> /usr/lib/dovecot/modules/lib20_fts_plugin.so(fts_search_lookup+0xeb) [0x7f5539b06bbb] -> /usr/lib/dovecot/modules/lib20_fts_plugin.so(+0xf8b8) [0x7f5539b088b8] -> dovecot/imap(imap_search_start+0x6a) [0x5654cb5a0d6a] -> dovecot/imap(cmd_sort+0x293) [0x5654cb593553] -> dovecot/imap(command_exec+0x64) [0x5654cb599874] -> dovecot/imap(+0x1bd22) [0x5654cb597d22] -> dovecot/imap(+0x1bdbc) [0x5654cb597dbc] -> dovecot/imap(client_handle_input+0x1b5) [0x5654cb5981c5] -> dovecot/imap(client_input+0xa4) [0x5654cb5987e4] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(io_loop_call_io+0x69) [0x7f553a8174a9] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x12e) [0x7f553a818d1e] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(io_loop_handler_run+0x4c) [0x7f553a8175ac] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f553a8177b8] -> /usr/lib/x86_64-linux-gnu/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f553a7940a3] -> dovecot/imap(main+0x339) [0x5654cb58a539] -> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7) [0x7f553a375b97] -> dovecot/imap(_start+0x2a) [0x5654cb58a71a]
Mar 14 23:14:58 *** dovecot: service=imap, user=***, ip=[::1]. Fatal: master: service(imap): child 6436 killed with signal 6 (core dumps disabled)

# 2.3.0.1 (ffd8a29): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.0.1 (d33dca20)
# OS: Linux 4.15.0-46-generic x86_64 Ubuntu 18.04.2 LTS ext4
auth_mechanisms = plain login digest-md5 cram-md5 apop
auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890&.-_@'
default_vsz_limit = 8096 M
disable_plaintext_auth = no
first_valid_uid = 30
imap_client_workarounds = delay-newmail
imap_logout_format = rcvd=%i, sent=%o
mail_home = /var/qmail/mailnames/%Ld/%Ln
mail_location = maildir:/var/qmail/mailnames/%Ld/%Ln/Maildir
mail_log_prefix = "service=%s, user=%u, ip=[%r]. "
mail_max_userip_connections = 100
mail_plugins = quota fts fts_squat virtual
managesieve_logout_format = rcvd=%i, sent=%o
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeri$
namespace inbox {
  inbox = yes
  location =
  prefix = INBOX.
  separator = .
}
namespace virtual {
  hidden = no
  inbox = no
  list = yes
  location = virtual:/var/qmail/mailnames/%Ld/%Ln/virtual/:INDEX=/var/qmail/mailnames/%Ld/%Ln/virtual/
  prefix =
  separator = .
}
passdb {
  driver = plesk
}
plugin {
  fts = squat
  fts_squat = partial=4 full=10
  quota = maildir:User quota
  quota_grace = 0
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
  sieve_extensions = +notify +imapflags
}
pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
pop3_logout_format = rcvd=%i, sent=%o, top=%t/%p, retr=%r/%b, del=%d/%m, size=%s
protocols = imap pop3 sieve
service auth-worker {
  group =
  user =
}
service auth {
  group =
  unix_listener auth-userdb {
    group = popuser
    mode = 0600
    user = popuser
  }
  user =
}
service imap-login {
  process_limit = 2048
  service_count = 1
}
service imap {
  process_limit = 2048
  service_count = 1
}
service pop3-login {
  process_limit = 2048
  service_count = 1
}
service pop3 {
  process_limit = 2048
  service_count = 1
}
ssl_cert = </etc/dovecot/private/dovecot.pem
ssl_cipher_list = HIGH:!aNULL:!MD5
ssl_dh =  # hidden, use -P to show it
ssl_key =  # hidden, use -P to show it
ssl_prefer_server_ciphers = yes
userdb {
  args = uid=popuser gid=popuser
  driver = static
}
protocol imap {
  mail_plugins = quota fts fts_squat virtual imap_quota
}
protocol pop3 {
  pop3_uidl_format = UID%u-%v
}
protocol sieve {
  mail_plugins = quota fts fts_squat virtual
}
protocol lda {
  mail_plugins = quota fts fts_squat virtual sieve
}