Delivery Temporarily Suspended Unknown Mail Transport Error Postfix Upd -

sudo tail -100 /var/log/mail.log # or on RHEL/CentOS: /var/log/maillog

Useful commands

The Postfix error "delivery temporarily suspended: unknown mail transport error" typically indicates that Postfix is attempting to use a delivery agent (transport) that it does not recognize or that is incorrectly defined in its configuration files. sudo tail -100 /var/log/mail