Error «no IP address found for host __LOCAL_IP__» when sending emails

Symptoms

Messages cannot be sent, an error of the following format appears in the Exim mail server log at /var/log/exim/mainlog:

no IP address found for host __LOCAL_IP__ (during SMTP connection from (hostname) [ip-address])

Causes

The server's local IP address is not specified in the hostlist relay_from_hosts directive in the Exim mail server configuration.

Solution

In the configuration file at /etc/exim4/exim4.conf.template, change the __LOCAL_IP__ value in the hostlist relay_from_hosts directive to the server's IP address.