Dovecot 2.3.2 still has the same issue we reported for 2.3.X:

Jul 05 15:10:49 lmtp(2730445): Panic: file lib-event.c: line 182 (event_pop_global): assertion failed: (event != NULL) Jul 05 15:10:49 lmtp(2730445): Error: Raw backtrace: /usr/lib/dovecot/libdovecot.so.0(+0xce054) [0x7f7f7c92f054] -> /usr/lib/dovecot/libdovecot.so.0(default_fatal_handler+0x2a) [0x7f7f7c92f09a] -> /usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f7f7c89e444] -> /usr/lib/dovecot/libdovecot.so.0(+0xe9e42) [0x7f7f7c94ae42] -> /usr/lib/dovecot/libdovecot-storage.so.0(+0x4ff88) [0x7f7f7cc2cf88] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_context_deactivate+0x5d) [0x7f7f7c94670d] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x85) [0x7f7f7c946b05] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x10f) [0x7f7f7c9483df] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0x52) [0x7f7f7c946be2] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f7f7c946e08] -> /usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f7f7c8c2783] -> dovecot/lmtp local READY [0x7f7f7d3634b9] -> /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f7f7c4b63d5] -> dovecot/lmtp local READY [0x7f7f7d3635e5]

gdb: Core was generated by `dovecot/lmtp [lo'. Program terminated with signal 6, Aborted. #0 0x00007f6502506207 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 56 return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig); (gdb) bt full #0 0x00007f6502506207 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 resultvar = 0 pid = 2826461 selftid = 2826461 #1 0x00007f65025078f8 in __GI_abort () at abort.c:90 save_stage = 2 act = {__sigaction_handler = {sa_handler = 0x1, sa_sigaction = 0x1}, sa_mask = {__val = { 520, 173, 140071844479056, 513, 140071811839987, 257, 140071844479056, 513, 7749847442339820800, 140071844479056, 140071812055443, 140071844479056, 140727678224992, 140071844567296, 140071812055801, 140071844479056}}, sa_flags = 43400170, sa_restorer = 0x7ffdb7454a01} sigs = {__val = {32, 0 <repeats 15 times>}} #2 0x00007f650296b01b in default_fatal_finish (type=<optimized out>, status=status@entry=0) at failures.c:247 backtrace = 0x7f6504888088 "/usr/lib/dovecot/libdovecot.so.0(+0xce054) [0x7f650296b054] -> /usr/lib/dovecot/libdovecot.so.0(default_fatal_handler+0x2a) [0x7f650296b09a] -> /usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f65028da"... recursed = 0 #3 0x00007f650296b09a in default_fatal_handler (ctx=0x7ffdb7454ad0, format=<optimized out>, args=<optimized out>) at failures.c:261 status = 0 #4 0x00007f65028da444 in i_panic ( format=format@entry=0x7f65029a6fa8 "file %s: line %d (%s): assertion failed: (%s)") at failures.c:325 ctx = {type = LOG_TYPE_PANIC, exit_status = 0, timestamp = 0x0, timestamp_usecs = 0, log_prefix = 0x0} args = {{gp_offset = 40, fp_offset = 48, overflow_arg_area = 0x7ffdb7454bc0, reg_save_area = 0x7ffdb7454b00}} #5 0x00007f6502986e42 in event_pop_global (event=<optimized out>) at lib-event.c:182 __func__ = "event_pop_global" #6 0x00007f6502c68f88 in mail_storage_service_io_deactivate_user_cb (user=0x7f65048e4708) at mail-storage-service.c:823 ---Type <return> to continue, or q <return> to quit--- event = 0x0 __func__ = "mail_storage_service_io_deactivate_user_cb" #7 0x00007f650298270d in io_loop_context_deactivate (ctx=0x7f65048df850) at ioloop.c:1054 cb_end = 0x7f65048e78f0 cb = 0x7f65048e78d0 __func__ = "io_loop_context_deactivate" #8 0x00007f6502982b05 in io_loop_call_io (io=0x7f650489d8c0) at ioloop.c:680 ioloop = 0x7f6504890c60 t_id = 0 __func__ = "io_loop_call_io" #9 0x00007f65029843df in io_loop_handler_run_internal (ioloop=ioloop@entry=0x7f6504890c60) at ioloop-epoll.c:222 ctx = 0x7f650489c200 list = 0x7f650489d920 io = <optimized out> tv = {tv_sec = 2147483, tv_usec = 0} events_count = <optimized out> msecs = <optimized out> ret = 1 i = 0 call = <optimized out> __func__ = "io_loop_handler_run_internal" #10 0x00007f6502982be2 in io_loop_handler_run (ioloop=ioloop@entry=0x7f6504890c60) at ioloop.c:726 __func__ = "io_loop_handler_run" #11 0x00007f6502982e08 in io_loop_run (ioloop=0x7f6504890c60) at ioloop.c:699 __func__ = "io_loop_run" #12 0x00007f65028fe783 in master_service_run (service=0x7f6504890af0, callback=callback@entry=0x7f650339f6e0 <client_connected>) at master-service.c:767 No locals. #13 0x00007f650339f4b9 in main (argc=2, argv=0x7f6504890890) at main.c:158 set_roots = {0x7f6502c0dea0 <smtp_submit_setting_parser_info>, 0x7f6503173ba0 <lda_setting_parser_info>, 0x7f65035a5500 <lmtp_setting_parser_info>, 0x0} ---Type <return> to continue, or q <return> to quit--- service_flags = <optimized out> storage_service_flags = <optimized out> tmp_base_dir = 0x7f6504888040 "\003" c = <optimized out> error = 0x0

-- Best regards, Martynas Bendorius