Seen this error a few times from dovecot-1.1.14, Mac OS X, 64-bit
Intel. NFS may have been used.

Panic: IMAP(user): file mail-index-sync-update.c: line 843
(mail_index_sync_map): assertion failed: (map->hdr.indexid == index-

indexid || map->hdr.indexid == 0)

Two different backtraces to this error are:

0 libSystem.B.dylib 0x00007fff87b775ea __kill + 10 1 libSystem.B.dylib 0x00007fff87bf9fc8 abort + 83 2 imap 0x0000000100069f3e
default_fatal_finish + 70 3 imap 0x0000000100069f8c
i_syslog_fatal_handler + 0 4 imap 0x00000001000696eb i_info + 0 5 imap 0x0000000100051d3a
mail_index_sync_map + 144 6 imap 0x000000010004a22c mail_index_map +
212 7 imap 0x0000000100046a0f
mail_index_refresh + 14 8 imap 0x0000000100016e4b
maildir_sync_header_refresh + 24 9 imap 0x0000000100016ee6
maildir_sync_quick_check + 61 10 imap 0x000000010001796a
maildir_sync_context + 91 11 imap 0x0000000100017d8e
maildir_storage_sync_init + 104 12 imap 0x000000010003eb1b mailbox_sync + 31 13 imap 0x00000001000048a8 cmd_select_full

• 224 14 imap 0x00000001000049f3 cmd_select + 11 15 imap 0x000000010000677e
  client_command_input + 33 16 imap 0x000000010000693f
  client_command_input + 482 17 imap 0x0000000100006a3e
  client_handle_input + 239 18 imap 0x0000000100006bc2 client_input + 148 19 imap 0x0000000100070f83
  io_loop_handler_run + 272 20 imap 0x0000000100070348 io_loop_run + 55 21 imap 0x000000010000db95 main + 1635 22 imap 0x0000000100001010 start + 52

0 libSystem.B.dylib 0x00007fff863125ea __kill + 10 1 libSystem.B.dylib 0x00007fff86394fc8 abort + 83 2 deliver 0x000000010005f82d
default_fatal_finish + 70 3 deliver 0x000000010005f8fb
i_set_failure_syslog + 0 4 deliver 0x000000010005efda i_info + 0 5 deliver 0x000000010004867e
mail_index_sync_map + 144 6 deliver 0x0000000100040b70
mail_index_map + 212 7 deliver 0x000000010003d353
mail_index_refresh + 14 8 deliver 0x0000000100044219
mail_index_transaction_commit_v + 988 9 deliver 0x0000000100032e1c
index_transaction_finish_commit + 90 10 deliver 0x000000010000fc4d
maildir_transaction_commit + 130 11 deliver 0x0000000100032cb9
index_transaction_commit + 63 12 lib10_quota_plugin.so 0x000000010021efd9
quota_get_mail_user_quota + 1907 13 deliver 0x00000001000354ac
mailbox_transaction_commit + 48 14 deliver 0x0000000100001844
deliver_save + 572 15 deliver 0x0000000100003244 main + 6266 16 deliver 0x0000000100000948 start + 52