Dovecot-2.0.alpha3's imap-login segfaulted with this backtrace: 0 hex_to_binary 1 master_send_request 2 anvil_input 3 io_loop_handler_run 4 io_loop_run 5 master_service_run 6 main 7 start Looks to me like auth_client_get_cookie() returned NULL in master_send_request().