diff --git a/core/includes/common.inc b/core/includes/common.inc
index 20d24a7..9721930 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1085,7 +1085,8 @@ function _drupal_http_use_proxy($host) {
 /**
  * Verifies the syntax of the given e-mail address.
  *
- * See @link http://tools.ietf.org/html/rfc5321 RFC 5321 @endlink for details.
+ * This uses the
+ * @link http://php.net/manual/filter.filters.validate.php PHP e-mail validation filter. @endlink
  *
  * @param $mail
  *   A string containing an e-mail address.
diff --git a/core/includes/mail.inc b/core/includes/mail.inc
index 25235f9..ebbd4c1 100644
--- a/core/includes/mail.inc
+++ b/core/includes/mail.inc
@@ -92,7 +92,9 @@
  *   will be {$module}_{$key}.
  * @param $to
  *   The e-mail address or addresses where the message will be sent to. The
- *   formatting of this string must comply with RFC 2822. Some examples are:
+ *   formatting of this string will be validated with the
+ *   @link http://php.net/manual/filter.filters.validate.php PHP e-mail validation filter. @endlink
+ *   Some examples are:
  *   - user@example.com
  *   - user@example.com, anotheruser@example.com
  *   - User <user@example.com>
diff --git a/core/lib/Drupal/Core/Mail/MailInterface.php b/core/lib/Drupal/Core/Mail/MailInterface.php
index e18ba5a..3485cfd 100644
--- a/core/lib/Drupal/Core/Mail/MailInterface.php
+++ b/core/lib/Drupal/Core/Mail/MailInterface.php
@@ -31,19 +31,21 @@ public function format(array $message);
    *   - id: A unique identifier of the e-mail type. Examples: 'contact_user_copy',
    *     'user_password_reset'.
    *   - to: The mail address or addresses where the message will be sent to.
-   *     The formatting of this string must comply with RFC 2822. Some examples:
+   *     The formatting of this string will be validated with the
+   *     @link http://php.net/manual/filter.filters.validate.php PHP e-mail validation filter. @endlink
+   *     Some examples:
    *     - user@example.com
    *     - user@example.com, anotheruser@example.com
    *     - User <user@example.com>
    *     - User <user@example.com>, Another User <anotheruser@example.com>
-   *    - subject: Subject of the e-mail to be sent. This must not contain any
-   *      newline characters, or the mail may not be sent properly.
-   *    - body: Message to be sent. Accepts both CRLF and LF line-endings.
-   *      E-mail bodies must be wrapped. You can use drupal_wrap_mail() for
-   *      smart plain text wrapping.
-   *    - headers: Associative array containing all additional mail headers not
-   *      defined by one of the other parameters.  PHP's mail() looks for Cc
-   *      and Bcc headers and sends the mail to addresses in these headers too.
+   *   - subject: Subject of the e-mail to be sent. This must not contain any
+   *     newline characters, or the mail may not be sent properly.
+   *   - body: Message to be sent. Accepts both CRLF and LF line-endings.
+   *     E-mail bodies must be wrapped. You can use drupal_wrap_mail() for
+   *     smart plain text wrapping.
+   *   - headers: Associative array containing all additional mail headers not
+   *     defined by one of the other parameters.  PHP's mail() looks for Cc and
+   *     Bcc headers and sends the mail to addresses in these headers too.
    *
    * @return bool
    *   TRUE if the mail was successfully accepted for delivery, otherwise FALSE.