Generally it's required to have a public IP address to be able to send email. This is only available for paid accounts, and prevents SPAMmers from using the platform.

However, if you have a clustered environment the public IP is assigned to the load balancer node (not the application containers). In this case please contact support and we will enable sendmail for you on your app servers in your user settings. This enables the application servers to send mail without needing a public IP specifically assigned to them.

This is only available if you have a public IP address on your load balancer in a clustered environment.

If your environment is not clustered, simply adding a public IP on the application server node will automatically enable sendmail.