API Developer Portal 4.2 can be configured to use an external SMTP server along with the product documentation on docops.ca.com.
Our Portal 4.2 has been configured to use an external SMTP server but any emails are not delivered for user sign-up.
The following warning message was recorded in the docker.log:
WARNING: 4: Unable to send email: Unknown SMTP host: smtp.domainname.local. Exception caught!
DNS cannot be used in this environment for hostname resolution.
API Portal 4.2 is relying on DNS for hostname resolution. Please configure DNS to be used for resolving hostnames.
The external SMTP server can be specified with its IP address instead of the hostname. It's a workaround.
The external SMTP server has to be configured to accept STARTTLS.