Can you post
gdb /usr/libexec/dovecot/lmtp /path/to/core bt full
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1 Copyright (C) 2016 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...(no debugging symbols found)...done. [New LWP 1910] Core was generated by `dovecot/lmtp'. Program terminated with signal SIGSEGV, Segmentation fault. #0 0x00007fb9c915aa71 in i_stream_seek () from /usr/lib/dovecot/libdovecot.so.0 (gdb) bt full #0 0x00007fb9c915aa71 in i_stream_seek () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #1 0x00007fb9c915dd6f in ?? () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #2 0x00007fb9c915ab83 in i_stream_read () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #3 0x00007fb9c91620ad in ?? () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #4 0x00007fb9c91622ab in ?? () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #5 0x00007fb9c915ab83 in i_stream_read () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #6 0x00007fb9c915b5cd in i_stream_read_data () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #7 0x00007fb9c9124a24 in ?? () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #8 0x00007fb9c912560e in ?? () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #9 0x00007fb9c91721d8 in ?? () from /usr/lib/dovecot/libdovecot.so.0 ---Type <return> to continue, or q <return> to quit--- No symbol table info available. #10 0x00007fb9c91649c2 in io_loop_call_io () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #11 0x00007fb9c9166039 in io_loop_handler_run_internal () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #12 0x00007fb9c9164a5c in io_loop_handler_run () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #13 0x00007fb9c9164c08 in io_loop_run () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #14 0x00007fb9c90ec983 in master_service_run () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #15 0x000055f6535b4d14 in main () No symbol table info available. (gdb) q
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