diff --git a/core/lib/Drupal/Core/Mail/MailManager.php b/core/lib/Drupal/Core/Mail/MailManager.php
index 7e1bd9de46..348dceeb20 100644
--- a/core/lib/Drupal/Core/Mail/MailManager.php
+++ b/core/lib/Drupal/Core/Mail/MailManager.php
@@ -249,9 +249,11 @@ public function doMail($module, $key, $to, $langcode, $params = [], $reply = NUL
     // Return-Path headers should have a domain authorized to use the
     // originating SMTP server.
     $headers['Sender'] = $headers['Return-Path'] = $site_mail;
-    // Headers are encoded in MailManager::doMail(). The site name must be
-    // encoded here to prevent doMail() from encoding the email address, which
-    // would break the header.
+    // Headers are usually encoded in the mail plugin that implements
+    // \Drupal\Core\Mail\MailInterface::mail(), for example,
+    // \Drupal\Core\Mail\Plugin\Mail\PhpMail::mail(). The site name must be
+    // encoded here to prevent mail plugins from encoding the email address,
+    // which would break the header.
     $headers['From'] = Unicode::mimeHeaderEncode($site_config->get('name'), TRUE) . ' <' . $site_mail . '>';
     if ($reply) {
       $headers['Reply-to'] = $reply;