Error: Call to undefined method

src/Plugin/Mail/Mail.php

@@ -277,7 +277,7 @@ class Mail implements MailInterface {
     $filename = basename($path);
     $file_buffer = file_get_contents($path);
     $file_buffer = chunk_split(base64_encode($file_buffer), 76, "\n");
-    $mime_type = $this->mimeTypeGuesser->guess($path);
+    $mime_type = $this->mimeTypeGuesser->guessMimeType($path);
     if (!$this->isValidContentType($mime_type)) {
       throw new \Exception($mime_type . ' is not a valid content type.');
     }