[Dovecot] Segmentation fault in dovecot director lmtp service

Hi,

the lmtp service of our dovecot director installation quits with a
segmentation fault if a lot of mails are simultaneously delivered.
For example if the postfix mailqueue is filled (for whatever reason)
and postqueue -f is run the lmtp service quits with a segmentation
fault:


Program terminated with signal 11, Segmentation fault.

#0  o_stream_cork (stream=0x0) at ostream.c:75

75              if (unlikely(stream->closed))

(gdb) backtrace

#0  o_stream_cork (stream=0x0) at ostream.c:75

#1  0x00007fa6e6af45d9 in lmtp_client_send_more (client=0x2435870)
at lmtp-client.c:596

#2  0x0000000002434170 in ?? ()

#3  0x00000000004070d9 in proxy_send_more (proxy=0x2435870) at
lmtp-proxy.c:390

#4  lmtp_proxy_data_input (proxy=0x2435870) at lmtp-proxy.c:444

#5  0x00007fa6e6af456f in lmtp_client_send_data (client=0x24347a0)
at lmtp-client.c:306

#6  0x0000000002434f98 in ?? ()

#7  0xffffffffe6af73c5 in ?? ()

#8  0x0000000002434840 in ?? ()

#9  0x0000000000000000 in ?? ()


I don't have any ideas why the stream is 0. The configuration of the
dovecot director installation is attached. Please let me know if i
shall provide any more information or test something.


Kind regards

Reinhard