It is hardcoded in the Plesk backend that the IP address for outgoing mail in the Postfix configuration file ( /etc/postfix/master.cf ) will be the same as the.
Please follow the tutorial posted for you. It explains clearly how to use external mail servers.
Unless you're looking for a set up similar to my setup, users connect to my Plesk mail server which then relays through an external mail server. Download Free Watchtower Bound Volumes Pdf To Word. If this is the case you need to manually add that capability in the postfix config file. There's many guides for this available, use your Google-Fu! Caution: Manually editing the Postfix config file has potential to seriously break things, if you're not sure what you're doing you should leave it alone and have a qualified sys-admin carry out the work.