in js/newsletters/filter.js [1:12]
exports.getUniqueEmails = function(groups, firstEmail) {
var userEmails = [firstEmail];
groups.forEach(function(group) {
group.users.forEach(function(user) {
var email = user.email;
if (email && userEmails.indexOf(email) < 0) {
userEmails.push(email);
}
})
});
return userEmails;
};