If you would like to add specific hosts to all domains that have SPF enabled, you can do so in WHM using the Exim Configuration Manager feature. This procedure will add the SPF hosts for new account creations as well.
- Log into WHM and navigate to "Home / Service Configuration / Exim Configuration Manager"
- In Basic Editor, click the Mail tab
- At setting "SPF include hosts for all domains on this system" click the radio button for the empty text box.
- Enter the comma-separated hosts.
- Scroll down and click Save
Please note there is an additional SPF setting here as well. The "Autodiscovery SPF include hosts from the smarthost route list" setting will apply if smarthost support is used with a route_list configured.