diff --git a/mailpoet/lib/API/JSON/v1/Services.php b/mailpoet/lib/API/JSON/v1/Services.php
index 5c6aacdc36..7e9b83657d 100644
--- a/mailpoet/lib/API/JSON/v1/Services.php
+++ b/mailpoet/lib/API/JSON/v1/Services.php
@@ -111,6 +111,8 @@ class Services extends APIEndpoint {
     $successMessage = null;
     if ($state == Bridge::KEY_VALID) {
       $successMessage = __('Your MailPoet Sending Service key has been successfully validated', 'mailpoet');
+    } else if ($state == Bridge::KEY_VALID_UNDERPRIVILEGED) {
+      $successMessage = __('Your Premium key has been successfully validated, but is not valid for MailPoet Sending Service', 'mailpoet');
     } elseif ($state == Bridge::KEY_EXPIRING) {
       $successMessage = sprintf(
         // translators: %s is the expiration date.
@@ -175,6 +177,8 @@ class Services extends APIEndpoint {
     $successMessage = null;
     if ($state == Bridge::KEY_VALID) {
       $successMessage = __('Your Premium key has been successfully validated', 'mailpoet');
+    } else if ($state == Bridge::KEY_VALID_UNDERPRIVILEGED) {
+      $successMessage = __('Your Premium key has been successfully validated, but is not valid for MailPoet Sending Service', 'mailpoet');
     } elseif ($state == Bridge::KEY_EXPIRING) {
       $successMessage = sprintf(
         // translators: %s is the expiration date.
diff --git a/mailpoet/lib/Services/Bridge.php b/mailpoet/lib/Services/Bridge.php
index d389fa506b..ddacbbdf66 100644
--- a/mailpoet/lib/Services/Bridge.php
+++ b/mailpoet/lib/Services/Bridge.php
@@ -23,6 +23,7 @@ class Bridge {
   const KEY_INVALID = 'invalid';
   const KEY_EXPIRING = 'expiring';
   const KEY_ALREADY_USED = 'already_used';
+  const KEY_VALID_UNDERPRIVILEGED = 'valid_underprivileged';
 
   const KEY_CHECK_ERROR = 'check_error';
 
@@ -235,7 +236,7 @@ class Bridge {
       200 => self::KEY_VALID,
       401 => self::KEY_INVALID,
       402 => self::KEY_ALREADY_USED,
-      403 => self::KEY_INVALID,
+      403 => self::KEY_VALID_UNDERPRIVILEGED,
     ];
 
     if (!empty($result['code']) && isset($stateMap[$result['code']])) {