Mass-emailing people?

[inotabi]

I have the same problem when i try to restrict sending mail to mailing list from external domain. I have followed the instructions (step by step) in RestrictPostfixRecipients title of wiki but it doesn't work for me. I have used postconf command to modify the parameters:
permitted_senders_list = check_sender_access hash:/opt/zimbra/postfix/conf/permitted_senders, reject
smtpd_restriction_classes = permitted_senders_list

however, when i use postconf to view the configuration information, i only "smtpd_restriction_classes = permitted_senders_list" in listing, not see "permitted_senders_list = check_sender_access hash:/opt/zimbra/postfix/conf/permitted_senders, reject". Who can help me to find out the problem? I have searched on forum but i don't see any solutions clearly.

if i use "smtpd_sender_restrictions = hash:/opt/zimbra/postfix/conf/permitted_senders, reject", it operates very well. However, when i use this option, it will deny all email from external. So, i must manually modify to permit the external domains sending email. I only want to restrict sending email from external domains to mailing lists. (I'm on FOSS 4.5.7)

Best regards,