Hi there The above error occurs when sending the 2nd, 3rd, 4th etc mail after authenticating (SMTP AUTH PLAIN), using both mail clients Thunderbird 2.0.0.14 and Opera 9.24. I have to restart qpsmtpd before being able to send again. ie. I'm only able to send without error the first time, or occasionally twice. Any pointers regarding a solution would be appreciated. config/plugins: hosts_allow dont_require_anglebrackets check_earlytalker action deny count_unrecognized_commands 4 check_relay tls ssl/server.crt ssl/server.key ssl/ca.crt require_resolvable_client at_connect 1 permfail 0 forward_lookup 0 dnsbl disconnect check_spamhelo auth/auth_checkcdb check_moregoodrcptto rcpt_ok virus/clamdscan2 clamd_socket /var/tmp/clamd.socket max_msg_size 10240 queue/qmail-queue I wrote the following plugins. auth/auth_checkcdb - http://pastie.org/237855 check_moregoodrcptto - http://pastie.org/237853 virus/clamdscan2 - http://pastie.org/237858 Thanks DaleThread Next