On the right side, you will have an options bar like the one shown in the image, go to the Whitelist / Blacklist panel and select the sender option.
This window will be displayed, just go to the add container button and a small menu will be displayed at the top of the page.
In “local-part” add the name of the email to be added and in “address” the name of the domain.
For example. If you need to add an email called firstname.lastname@example.org, then the configuration would be as follows.
Local-part = test
Address = gmail.com
Note: Important to check the “Apply to both” option Once done, press the “Save” button