From the log:

Jun 5 16:38:46 postamt dovecot: imap-login: Login: user=<username>, method=PLAIN, rip=141.42.142.67, lip=141.42.4.250 Jun 5 16:38:49 postamt dovecot: IMAP(username): Panic: Trying to sync mailbox Sent with open transactions Jun 5 16:38:49 postamt dovecot: IMAP(username): Raw backtrace: imap [0x80f0381] -> imap [0x80f0402] -> imap [0x80efd89] -> imap [0x80b5084] -> imap(imap_sync_init+0x54) [0x806fd24] -> imap [0x80623d2] -> imap(cmd_idle+0x119) [0x8062539] -> imap [0x806734c] -> imap [0x80673f3] -> imap(client_handle_input+0x2d) [0x806754d] -> imap(client_input+0x5f) [0x8067eaf] -> imap(io_loop_handler_run+0xe0) [0x80f8f90] -> imap(io_loop_run+0x20) [0x80f8400] -> imap(main+0x5f5) [0x80708b5] -> /lib/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb7ded775] -> imap [0x805fcb1] Jun 5 16:38:49 postamt dovecot: IMAP(username): Connection closed bytes=101/783

The backtrace:

GNU gdb 6.8-debian Copyright (C) 2008 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i486-linux-gnu"... Reading symbols from /lib/i686/cmov/libdl.so.2...Reading symbols from /usr/lib/debug/lib/i686/cmov/libdl-2.9.so...done. done. Loaded symbols for /lib/i686/cmov/libdl.so.2 Reading symbols from /lib/i686/cmov/libc.so.6...Reading symbols from /usr/lib/debug/lib/i686/cmov/libc-2.9.so...done. done. Loaded symbols for /lib/i686/cmov/libc.so.6 Reading symbols from /lib/ld-linux.so.2...Reading symbols from /usr/lib/debug/lib/ld-2.9.so...done. done. Loaded symbols for /lib/ld-linux.so.2 Reading symbols from /usr/local/lib/dovecot/imap/lib10_quota_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib10_quota_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib11_imap_quota_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib11_imap_quota_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib11_trash_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib11_trash_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib20_autocreate_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib20_autocreate_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib20_fts_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib20_fts_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib20_mail_log_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib20_mail_log_plugin.so Reading symbols from /usr/local/lib/dovecot/imap/lib20_zlib_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib20_zlib_plugin.so Reading symbols from /usr/lib/libz.so.1...done. Loaded symbols for /usr/lib/libz.so.1 Reading symbols from /lib/libbz2.so.1.0...done. Loaded symbols for /lib/libbz2.so.1.0 Reading symbols from /usr/local/lib/dovecot/imap/lib21_fts_squat_plugin.so...done. Loaded symbols for /usr/local/lib/dovecot/imap/lib21_fts_squat_plugin.so Reading symbols from /usr/lib/gconv/ISO8859-1.so...Reading symbols from /usr/lib/debug/usr/lib/gconv/ISO8859-1.so...done. done. Loaded symbols for /usr/lib/gconv/ISO8859-1.so Reading symbols from /usr/lib/gconv/ISO8859-15.so...Reading symbols from /usr/lib/debug/usr/lib/gconv/ISO8859-15.so...done. done. Loaded symbols for /usr/lib/gconv/ISO8859-15.so Reading symbols from /lib/libgcc_s.so.1...done. Loaded symbols for /lib/libgcc_s.so.1 Core was generated by `imap [username 141.42.142.67]'. Program terminated with signal 6, Aborted. [New process 11429] #0 0xb7f47424 in __kernel_vsyscall () #0 0xb7f47424 in __kernel_vsyscall () No symbol table info available. #1 0xb7e02680 in *__GI_raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64 resultvar = <value optimized out> pid = -1208799244 selftid = 11429 #2 0xb7e05d68 in *__GI_abort () at abort.c:88 act = {__sigaction_handler = {sa_handler = 0x9ed64b8, sa_sigaction = 0x9ed64b8}, sa_mask = {__val = {3214921832, 135193146, 3086165728, 0, 3214921952, 3214921940, 512, 0, 0, 3214922016, 3086374512, 134566059, 516, 0, 0, 0, 1, 135263934, 512, 1, 3214921940, 166552728, 69, 3214922068, 3214921912, 135194742, 166553276, 3214921940, 3214921944, 517, 166552760, 3085608163}}, sa_flags = 517, sa_restorer = 0x81052f9 } sigs = {__val = {32, 0 }} #3 0x080f0395 in default_fatal_finish (type=<value optimized out>, status=0) at failures.c:160 backtrace = 0x9ed6288 "imap [0x80f0381] -> imap [0x80f0402] -> imap [0x80efd89] -> imap [0x80b5084] -> imap(imap_sync_init+0x54) [0x806fd24] -> imap [0x80623d2] -> imap(cmd_idle+0x119) [0x8062539] -> imap [0x806734c] -> ima"... #4 0x080f0402 in i_internal_fatal_handler (type=LOG_TYPE_PANIC, status=0, fmt=0x8112614 "Trying to sync mailbox %s with open transactions", args=0xbf9fd1b4 "\030��\t��\237�$�\006\bX��\t") at failures.c:440 No locals. #5 0x080efd89 in i_panic ( format=0x8112614 "Trying to sync mailbox %s with open transactions") at failures.c:207 No locals. #6 0x080b5084 in mailbox_sync_init (box=0x9eeae58, flags=6) at mail-storage.c:543 No locals. #7 0x0806fd24 in imap_sync_init (client=0x9ee3360, box=0x9eeae58, imap_flags=0, flags=0) at imap-sync.c:146 ctx = (struct imap_sync_context *) 0xa23fae8 __PRETTY_FUNCTION__ = "imap_sync_init" #8 0x080623d2 in idle_sync_now (box=<value optimized out>, ctx=0x6) at cmd-idle.c:122 __PRETTY_FUNCTION__ = "idle_sync_now" #9 0x08062539 in cmd_idle (cmd=0x9ee36e8) at cmd-idle.c:243 client = (struct client *) 0x9ee3360 ctx = <value optimized out> str = <value optimized out> interval = <value optimized out> #10 0x0806734c in client_command_input (cmd=0x9ee36e8) at client.c:607 client = (struct client *) 0x9ee3360 command = <value optimized out> __PRETTY_FUNCTION__ = "client_command_input" #11 0x080673f3 in client_command_input (cmd=0x9ee36e8) at client.c:656 client = (struct client *) 0x9ee3360 command = <value optimized out> __PRETTY_FUNCTION__ = "client_command_input" #12 0x0806754d in client_handle_input (client=0x9ee3360) at client.c:697 _data_stack_cur_id = 3 ret = false remove_io = <value optimized out> handled_commands = false __PRETTY_FUNCTION__ = "client_handle_input" #13 0x08067eaf in client_input (client=0x9ee3360) at client.c:748 cmd = <value optimized out> output = (struct ostream *) 0x9ee3514 bytes = <value optimized out> __PRETTY_FUNCTION__ = "client_input" #14 0x080f8f90 in io_loop_handler_run (ioloop=0x9edfd88) at ioloop-epoll.c:208 ctx = (struct ioloop_handler_context *) 0x9edea80 event = (const struct epoll_event *) 0x9edeac0 list = (struct io_list *) 0x9ee3598 io = (struct io_file *) 0x9f1f3d0 tv = {tv_sec = 0, tv_usec = 0} t_id = 2 msecs = <value optimized out> ret = 1 i = 0 j = 0 call = <value optimized out> #15 0x080f8400 in io_loop_run (ioloop=0x9edfd88) at ioloop.c:338 No locals. #16 0x080708b5 in main (argc=) at main.c:323 No locals. $1 = {prev = 0x0, next = 0x9ee35f0, client = 0x9ee3360, pool = 0x9ee35d8, tag = 0x9ee3760 "420", name = 0x9ee3768 "IDLE", args = 0x0, cmd_flags = COMMAND_FLAG_BREAKS_SEQS, func = 0x80621f0 , context = 0x9ee3770, module_contexts = {arr = {buffer = 0x9ee3728, element_size = 4}, v = 0x9ee3728, v_modifiable = 0x9ee3728}, parser = 0xa1b24d8, state = CLIENT_COMMAND_STATE_WAIT_INPUT, sync = 0x0, uid = 0, cancel = 0, param_error = 0, search_save_result = 0, temp_executed = 0} $2 = {prev = 0x9ee36e8, next = 0x0, client = 0x9ee3360, pool = 0x9ee35d8, tag = 0x9ee3668 "419", name = 0x9ee3678 "UID SEARCH", args = 0x9ee3688 "UNDELETED BODY \"casa\"", cmd_flags = COMMAND_FLAG_BREAKS_SEQS, func = 0x806d690 , context = 0x9ee36a0, module_contexts = {arr = {buffer = 0x9ee3630, element_size = 4}, v = 0x9ee3630, v_modifiable = 0x9ee3630}, parser = 0x9ee85e0, state = CLIENT_COMMAND_STATE_WAIT_INPUT, sync = 0x0, uid = 1, cancel = 0, param_error = 0, search_save_result = 0, temp_executed = 0} (gdb) quit

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