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
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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