Injecting Using SMTP
The ESMTP Listener will accept any properly formatted SMTP connection request allowed by its configuration. For instance, based on this:
KumoMTA will accept any SMTP injection from the local host as well as any hosts in the 10.5.1.0/24 CIDR block on port 25. The most basic form of "injection" is to test from localhost using nc or telnet.
If that returns a
250 OK, then any more complex injection should work as well.
In most campaign systems that connect with third-party MTA's, you will need to enter the configuration settings, and find something like "SMTP" or "OutBound Email" and set the SMTP Port, Hostname or IP ddress and If you have configured SMTP_Auth, your injection username and password as well.
Below is a configuration screen for Ongage
And this is a sample of the configuration page for Mautic marketing automation.