I was unable to produce an IMAP core but have been successful with LMTP. Basically it crashes right upon login or delivery:
Dec 20 08:55:23 nihlus dovecot: master: Dovecot v2.2.devel (9bc8d9b) starting up for imap, lmtp Dec 20 08:56:15 nihlus dovecot: imap(tlx@leuxner.net): Fatal: master: service(imap): child 5710 killed with signal 11 (core not dumped) Dec 20 08:57:23 nihlus dovecot: lmtp(5967): Connect from local Dec 20 08:57:23 nihlus dovecot: lmtp(5967): Fatal: master: service(lmtp): child 5967 killed with signal 11 (core dumped)
$ gdb /usr/lib/dovecot/lmtp core_lmtp.5967.nihlus.leuxner.net GNU gdb (Debian 7.7.1+dfsg-5) 7.7.1 Copyright (C) 2014 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 "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from /usr/lib/dovecot/lmtp...Reading symbols from /usr/lib/debug/.build-id/ec/199069dd786feb54e5af43f983ce9c3bb4c29c.debug...done. done. [New LWP 5967] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Core was generated by `dovecot/lmtp'. Program terminated with signal SIGSEGV, Segmentation fault. #0 __memcpy_sse2_unaligned () at ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S:33 33 ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S: No such file or directory. #0 __memcpy_sse2_unaligned () at ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S:33 No locals. #1 0x00007f9177db4779 in memcpy (__len=<optimized out>, __src=0x0, __dest=0x7f917a5c5bf8) at /usr/include/x86_64-linux-gnu/bits/string3.h:51 No locals. #2 p_strconcat (pool=<optimized out>, str1=<optimized out>) at strfuncs.c:218 args = {{gp_offset = 16, fp_offset = 48, overflow_arg_area = 0x7ffdcadea060, reg_save_area = 0x7ffdcade9f90}} temp = 0x0 ret = <optimized out> len = 49 #3 0x00007f91780744fd in mdbox_storage_create (_storage=0x7f917a5c5930, ns=0x7f917a5b79d0, error_r=0x7ffdcadea1a0) at mdbox-storage.c:57 storage = 0x7f917a5c5930 dir = <optimized out> #4 0x00007f917805952b in mail_storage_create_full (ns=ns@entry=0x7f917a5b79d0, driver=<optimized out>, driver@entry=0x0, data=<optimized out>, flags=flags@entry=(unknown: 0), storage_r=storage_r@entry=0x7ffdcadea170, error_r=error_r@entry=0x7ffdcadea1a0) at mail-storage.c:395 storage = 0x7f917a5c5930 list = 0x7f917a5c3ca0 list_set = {layout = 0x7f91781083c6 "fs", root_dir = 0x7f917a52e100 "/var/vmail/domains/leuxner.net/tlx/mdbox", index_dir = 0x0, index_pvt_dir = 0x0, control_dir = 0x0, alt_dir = 0x0, inbox_path = 0x0, subscription_fname = 0x7f917810f234 "subscriptions", list_index_fname = 0x7f917810925e "dovecot.list.index", maildir_name = 0x7f917810bc17 "dbox-Mails", mailbox_dir_name = 0x7f917810c301 "mailboxes", escape_char = 0 '\000', broken_char = 0 '\000', utf8 = false, alt_dir_nocheck = false, index_control_use_maildir_name = false} list_flags = <optimized out> p = <optimized out> __FUNCTION__ = "mail_storage_create_full" #5 0x00007f91780598cc in mail_storage_create (ns=ns@entry=0x7f917a5b79d0, driver=driver@entry=0x0, flags=flags@entry=(unknown: 0), error_r=error_r@entry=0x7ffdcadea1a0) at mail-storage.c:416 storage = 0x7f917a5bfc90 #6 0x00007f9178051b89 in mail_namespaces_init_add (user=user@entry=0x7f917a5bfc90, ns_set=<optimized out>, unexpanded_ns_set=0x7f917a5c0178, ns_p=ns_p@entry=0x7ffdcadea200, error_r=error_r@entry=0x7ffdcadea290) at mail-namespace.c:195 mail_set = <optimized out> ns = 0x7f917a5b79d0 driver = 0x0 error = 0x0 ret = <optimized out> #7 0x00007f9178052cd9 in mail_namespaces_init (user=0x7f917a5bfc90, error_r=error_r@entry=0x7ffdcadea290) at mail-namespace.c:414 mail_set = 0x7f917a5c0c58 ns_set = 0x7f917a5c0f70 unexpanded_ns_set = 0x7f917a5c0150 namespaces = 0x0 ns_p = 0x7ffdcadea200 i = <optimized out> count = <optimized out> count2 = <optimized out> __FUNCTION__ = "mail_namespaces_init" #8 0x00007f9178060b65 in mail_storage_service_init_post (ctx=<optimized out>, error_r=0x7ffdcadea290, mail_user_r=<optimized out>, priv=0x7ffdcadea2a0, user=0x7f917a573910) at mail-storage-service.c:728 mail_set = 0x7f917a5c0c58 home = 0x7f917a59e761 "/var/vmail/domains/leuxner.net/tlx" mail_user = 0x7f917a5bfc90 #9 mail_storage_service_next_real (mail_user_r=<optimized out>, user=0x7f917a573910, ctx=<optimized out>) at mail-storage-service.c:1427 len = <optimized out> temp_priv_drop = <optimized out> priv = {uid = 5000, gid = 5000, uid_source = 0x7f9178107684 "userdb lookup", gid_source = 0x7f9178107684 "userdb lookup", home = 0x7f917a59e761 "/var/vmail/domains/leuxner.net/tlx", chroot = 0x7f917a52d458 ""} error = 0x7f917a5b3830 "" disallow_root = <optimized out> use_chroot = <optimized out> #10 mail_storage_service_next (ctx=<optimized out>, user=0x7f917a573910, mail_user_r=mail_user_r@entry=0x7f917a560b48) at mail-storage-service.c:1445 old_log_prefix = 0x7f917a5ba530 "lmtp(5967, tlx@leuxner.net): " #11 0x00007f9178789f55 in client_deliver (session=0x7f917a5bf880, src_mail=0x7f917a5bb060, rcpt=0x7f917a5621d0, client=0x7f917a560a10) at commands.c:837 set_parser = <optimized out> line = <optimized out> str = <optimized out> mail_error = 2052462064 ret = <optimized out> input = <optimized out> ns = <optimized out> delivery_time_started = {tv_sec = 1482220643, tv_usec = 129544} sets = <optimized out> storage = 0x7f917a5b3870 mail_set = <optimized out> username = 0x7f917a52d070 "tlx@leuxner.net" dctx = {pool = 0x0, set = 0x7f917a560a10, session = 0x0, timeout_secs = 0, session_time_msecs = 0, delivery_time_started = {tv_sec = 140262799447056, tv_usec = 140262799447168}, dup_ctx = 0x2, session_id = 0x7f9177d980d8 <i_stream_file_read+136> "H\211\305H\211\350H\301\350?\204\300D\017\266\350\017\205\030\001", src_mail = 0xf72, src_envelope_sender = 0xf65305b35804d500 <error: Cannot access memory at address 0xf65305b35804d500>, dest_user = 0x0, dest_addr = 0x7f917a561410 "\001", final_dest_addr = 0x7f917a561480 "q ", dest_mailbox_name = 0x2 <error: Cannot access memory at address 0x2>, dest_mail = 0x0, var_expand_table = 0x7f9177d93c33 <i_stream_read+83>, tempfail_error = 0x7f917a560a10 "", tried_default_save = 64, saved_mail = 71, save_dest_mail = 83, mailbox_full = 122, dsn = 145} lda_set = <optimized out> error = <optimized out> #12 client_deliver_next (session=0x7f917a5bf880, src_mail=0x7f917a5bb060, client=0x7f917a560a10) at commands.c:930 count = <optimized out> #13 client_input_data_write_local (input=<optimized out>, client=0x7f917a560a10) at commands.c:1026 src_mail = 0x7f917a5bb060 first_uid = 4294967295 session = 0x7f917a5bf880 old_uid = 0 #14 client_input_data_write (client=0x7f917a560a10) at commands.c:1161 input = 0x7f917a57d1f0 #15 client_input_data_handle (client=0x7f917a560a10) at commands.c:1256 data = <optimized out> size = 110 ret = <optimized out> #16 0x00007f9177d9d962 in io_loop_call_io (io=0x7f917a5615f0) at ioloop.c:599 ioloop = 0x7f917a534740 t_id = 2 __FUNCTION__ = "io_loop_call_io" #17 0x00007f9177d9efba in io_loop_handler_run_internal (ioloop=ioloop@entry=0x7f917a534740) at ioloop-epoll.c:222 ctx = 0x7f917a53a370 io = <optimized out> tv = {tv_sec = 299, tv_usec = 984106} events_count = <optimized out> msecs = <optimized out> ret = 1 i = 0 j = <optimized out> call = <optimized out> __FUNCTION__ = "io_loop_handler_run_internal" #18 0x00007f9177d9d9fc in io_loop_handler_run (ioloop=ioloop@entry=0x7f917a534740) at ioloop.c:648 No locals. #19 0x00007f9177d9dba8 in io_loop_run (ioloop=0x7f917a534740) at ioloop.c:623 __FUNCTION__ = "io_loop_run" #20 0x00007f9177d25a83 in master_service_run (service=0x7f917a5345e0, callback=<optimized out>) at master-service.c:641 No locals. #21 0x00007f9178788262 in main (argc=1, argv=0x7f917a534390) at main.c:125 set_roots = {0x7f917855e400 <lda_setting_parser_info>, 0x7f917898f580 <lmtp_setting_parser_info>, 0x0} service_flags = <optimized out> storage_service_flags = <optimized out> c = <optimized out>