Postfix errors: said: 451 Requested action aborted: local error in processing (in reply to MAIL FROM command))

    Hi all,
    I have a few clients with random errors like this from valid email addresses. The email obviously does not reach their mailbox.


    (host sender.com [x.x.x.x] said: 451 Requested action aborted: local error in processing (in reply to MAIL FROM command))


    This happens quiet randomly on various clients only. I'm using postscreen plugin but I was getting this same error before installing the plugin when I was using the standard IMCP config.



    Here is some of my /etc/postfix/main.cf


    # SASL parameters


    smtpd_sasl_auth_enable = yes


    smtpd_sasl_security_options = noanonymous


    broken_sasl_auth_clients = yes


    smtpd_sasl_authenticated_header = yes


    smtpd_helo_required = yes


    smtpd_helo_restrictions = permit_mynetworks,


    permit_sasl_authenticated,


    reject_invalid_helo_hostname,


    reject_non_fqdn_helo_hostname


    smtpd_sender_restrictions = reject_non_fqdn_sender,


    reject_unknown_sender_domain,


    permit_mynetworks,


    permit_sasl_authenticated


    smtpd_recipient_restrictions = reject_non_fqdn_recipient,


    reject_unknown_recipient_domain,


    permit_mynetworks,


    permit_sasl_authenticated,


    reject_unauth_destination,


    reject_unlisted_recipient,


    permit


    smtpd_data_restrictions = reject_multi_recipient_bounce,


    reject_unauth_pipelining



    Any ideas where this error is coming from?


    Thanks,
    Rob