Hi!
I got this error when build dovecot from source (rev 17627), configure it as imapc proxy (http://wiki2.dovecot.org/HowTo/ImapcProxy) and run imaptest with clients=2 or more, on latest stable version (2.2.13) and with clients=1 this error does not occurred.
Jul 16 17:22:26 imap(user771): Panic: file mail-index-sync-update.c: line 250 (sync_expunge_range): assertion failed: (count > 0) Jul 16 17:22:26 imap(user771): Error: Raw backtrace: /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(+0x872a6) [0x7f8a956682a6] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(+0x88683) [0x7f8a95669683] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f8a956685f9] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x106f13) [0x7f8a959f5f13] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x107e5a) [0x7f8a959f6e5a] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_sync_record+0x33) [0x7f8a959f76a3] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_sync_map+0x4e8) [0x7f8a959f7d97] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_map+0x126) [0x7f8a959e1817] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0xeb410) [0x7f8a959da410] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0xeb707) [0x7f8a959da707] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage. so.0(mail_index_open+0x17e) [0x7f8a959daa33] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(index_storage_mailbox_open+0xe7) [0x7f8a959c6742] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x81fd4) [0x7f8a95970fd4] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x9a5d4) [0x7f8a959895d4] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mailbox_open+0x1d) [0x7f8a9598975d] -> dovecot/imap() [0x414a3f] -> dovecot/imap(cmd_select_full+0x204) [0x414fac] -> dovecot/imap(cmd_select+0x1d) [0x414ff1] -> dovecot/imap(command_exec+0x5f) [0x41bdf4] -> dovecot/imap() [0x41ad47] -> dovecot/imap() [0x41b049] -> dovecot/imap() [0x41b169] -> dovecot/imap(client_handle_input+0x7e) [0x41b1e9] -> dovecot/imap(client_input+0xe6) [0x41b37c] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_call_io+0xb6) [0x7f8a95681c32] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x1e5) [0x7f8a95683ce4] -> /home/lion/dovecot-2.2/lib/ dovecot/libdovecot.so.0(io_loop_handler_run+0x18) [0x7f8a95681dcd] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_run+0xaf) [0x7f8a95681d26] Jul 16 17:22:26 imap(user771): Panic: file mail-index-sync-update.c: line 250 (sync_expunge_range): assertion failed: (count > 0) Jul 16 17:22:26 imap(user771): Error: Raw backtrace: /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(+0x872a6) [0x7fc4005942a6] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(+0x88683) [0x7fc400595683] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7fc4005945f9] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x106f13) [0x7fc400921f13] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x107e5a) [0x7fc400922e5a] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_sync_record+0x33) [0x7fc4009236a3] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_sync_map+0x4e8) [0x7fc400923d97] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mail_index_map+0x126) [0x7fc40090d817] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0xeb410) [0x7fc400906410] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0xeb707) [0x7fc400906707] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage. so.0(mail_index_open+0x17e) [0x7fc400906a33] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(index_storage_mailbox_open+0xe7) [0x7fc4008f2742] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x81fd4) [0x7fc40089cfd4] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(+0x9a5d4) [0x7fc4008b55d4] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot-storage.so.0(mailbox_open+0x1d) [0x7fc4008b575d] -> dovecot/imap() [0x414a3f] -> dovecot/imap(cmd_select_full+0x204) [0x414fac] -> dovecot/imap(cmd_select+0x1d) [0x414ff1] -> dovecot/imap(command_exec+0x5f) [0x41bdf4] -> dovecot/imap() [0x41ad47] -> dovecot/imap() [0x41b049] -> dovecot/imap() [0x41b169] -> dovecot/imap(client_handle_input+0x7e) [0x41b1e9] -> dovecot/imap(client_input+0xe6) [0x41b37c] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_call_io+0xb6) [0x7fc4005adc32] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x1e5) [0x7fc4005afce4] -> /home/lion/dovecot-2.2/lib/ dovecot/libdovecot.so.0(io_loop_handler_run+0x18) [0x7fc4005addcd] -> /home/lion/dovecot-2.2/lib/dovecot/libdovecot.so.0(io_loop_run+0xaf) [0x7fc4005add26]
# 2.2.13 (fd0616d553b0): /home/lion/dovecot-2.2/etc/dovecot/dovecot.conf # OS: Linux 3.11.0-24-generic x86_64 Ubuntu 12.04.4 LTS auth_mechanisms = plain login default_internal_user = lion default_login_user = lion disable_plaintext_auth = no imapc_host = localhost log_path = /home/lion/dovecot-2.2/var/log/dovecot.log mail_home = /home/lion/dovecot-2.2/home/vmail/%u mail_location = imapc:~/imapc namespace inbox { inbox = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { special_use = \Junk } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Trash { special_use = \Trash } prefix = } passdb { args = host=localhost port=143 default_fields = userdb_imapc_user=%u userdb_imapc_password=%w driver = imap } plugin { fts = solr fts_solr = url=http://localhost:8080/solr/ break-imap-search mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename mail_log_fields = uid box msgid size } service anvil { chroot = } service auth-worker { user = $default_internal_user } service imap-login { chroot = inet_listener imap { port = 10143 } inet_listener imaps { port = 10993 } } service lmtp { chroot = } service pop3-login { chroot = inet_listener pop3 { port = 10110 } inet_listener pop3s { port = 10995 } } ssl = no userdb { driver = prefetch }