Postfix ignore authentication

Question

Our ISP decided to redirect all connections destined to port 25 to their own servers, saying they are trying to combat spam. Fair enough, but this breaks authentication for all my clients as they authenticate to their own servers. I have tried with a few to change the port from 25 to 587 or even try and use SSL, but a few of them only accepts mail on port 25.

Now I have my own mail server meant only for sending mail from clients on my network, but how can I set up Postfix to ignore any authentication and just send the email since its coming from my network?

Below is the existing parts of importance in my setup:

mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 10.0.8.0/21
inet_interfaces = 10.0.15.251, 127.0.0.1    
smtpd_helo_required = yes
disable_vrfy_command = yes

smtpd_recipient_restrictions =
    warn_if_reject,
    reject_non_fqdn_sender,
    reject_non_fqdn_recipient,
    reject_unknown_sender_domain,
    reject_unknown_recipient_domain,
    permit_mynetworks,
    reject_unauth_destination,
    check_recipient_access pcre:/etc/postfix/recipient_checks.pcre,
    check_helo_access hash:/etc/postfix/helo_checks,
    check_sender_access hash:/etc/postfix/sender_checks,
    check_client_access hash:/etc/postfix/client_checks,
    check_client_access pcre:/etc/postfix/client_checks.pcre,
    permit

smtpd_data_restrictions =
    reject_unauth_pipelining,
    permit

This works fine when you don't use authentication, but I want it to pass mail through for people that have authentication enabled.

Thanks