Do not modify attachment content

Binary files do not like to have 0x0D 0x0A replaced with 0x0A

Author: jacekkow

src/MessagePart.php

@@ -99,6 +99,9 @@ public function getContentType(): string
 
     public function getContent(): string
     {
+        if ($this->isAttachment()) {
+            return $this->content;
+        }
         if (strtolower($this->getHeader('Content-Transfer-Encoding', '')) === 'base64') {
             return Utils::normaliseLineEndings(base64_decode($this->content));
         }