I don't know why postfix suddenly cannot send out email. I found that clamd.amavisd cannot start, I tried reinstall it and no luck. I know I must re-activate it but now more urgent is let my client send emails. I searched the whole night and found that Falko post comment out belows in main.cf #content_filter = amavis:[127.0.0.1]:10024 #receive_override_options = no_address_mappings After restart postfix, all emails still send through port 10024 and state, delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused all emails hold in queue. Then I also found another post to comment out master.cf #amavis unix - - - - 2 smtp # -o smtp_data_done_timeout=1200 # -o smtp_send_xforward_command=yes #127.0.0.1:10025 inet n - - - - smtpd # -o content_filter= # -o local_recipient_maps= # -o relay_recipient_maps= # -o smtpd_restriction_classes= # -o smtpd_client_restrictions= # -o smtpd_helo_restrictions= # -o smtpd_sender_restrictions= # -o smtpd_recipient_restrictions=permit_mynetworks,reject # -o mynetworks=127.0.0.0/8 # -o strict_rfc821_envelopes=yes # -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks # -o smtpd_bind_address=127.0.0.1 After that then restart postfix again, now it shows "mail transport unavailable". All emails still hold in queue. I think that ISP3 changed some settings in master.cf for amavis, and wiped out original master.cf settings. Can anyone help me what I have to add back in master.cf for normal transportation? Really very urgent!! Thanks so much!!