From JumpBox Documentation Wiki

Configure Email Relaying

In some situations you may want to use a relay server that you specify for email. For instance if you're hosting your JumpBox on your home internet connection, many providers will block outbound port 25 effectively killing your ability to send emails from your JumpBox. Using this Email Relaying feature you can configure a relay host and route email traffic through a server of your choosing.

1. Click the "Email" icon in the admin portal.

2. Choose the "configure host" option and specify the IP address or fully-qualified domain name of your email server. Click "Save."

If your mail relay requires authentication you cannot configure that through the JumpBox Administration Portal, please see our Authenticated Mail Relay FAQ.