Accept items with only address on mass import

The use of the mass import of realnames/emailadresses is not a daily task. You can use it for entering adresses by hand. For not all emailadresses the realname is known. A employee will not see it as a natural case to enter a ; before an address when the name not is available.
I recommend to change the simplenews_realname_subscription_list_add_submit() function from:

  foreach ($subscriptions as $subscription) {
    $realname = $subscription[0];
    $mail = trim($subscription[1]);
    if (valid_email_address($mail)) {
    ...

into

    $realname = $subscription[0];
    $mail = trim($subscription[1]);
    if (empty($subscription[1]) {
      $mail = $realname;
      $realname = '';
    }
    if (valid_email_address($mail)) {
    ...

The likelihood no name is entered is greater then no emailaddress. And if only a name is entered it will be flagged as a non-valid emailaddress.