diff -u b/core/modules/contact/src/ContactFormEditForm.php b/core/modules/contact/src/ContactFormEditForm.php
--- b/core/modules/contact/src/ContactFormEditForm.php
+++ b/core/modules/contact/src/ContactFormEditForm.php
@@ -118,12 +118,16 @@
     // Validate and each email recipient.
     $recipients = explode("\n", $form_state->getValue('recipients'));
 
-    foreach ($recipients as &$recipient) {
+    foreach ($recipients as $delta => &$recipient) {
       $recipient = trim($recipient);
       // Do not check empty lines.
       if ($recipient && !$this->emailValidator->isValid($recipient)) {
         $form_state->setErrorByName('recipients', $this->t('%recipient is an invalid email address.', array('%recipient' => $recipient)));
       }
+      elseif (empty($recipient)) {
+        // Clear empty lines.
+        unset($recipients[$delta]);
+      }
     }
     $form_state->setValue('recipients', $recipients);
   }