You will need to include an IF statement and can use the old way of writing to the tests tab (before Postman included the pm.expect library).
const response = pm.response.json();
let allowedDomains = ["somedomain.com","somedomain2.com"]
response.forEach(record => {
const emailDomain = record.email.split('@')[1];
console.log(emailDomain);
if (!allowedDomains.includes(emailDomain)) {
tests[`${emailDomain} is not in allowed list`] = false;
}
});