diff --git a/src/MDMailerHelper.php b/src/MDMailerHelper.php
index 213e2ae..bd0d02b 100644
--- a/src/MDMailerHelper.php
+++ b/src/MDMailerHelper.php
@@ -21,6 +21,10 @@ final class MDMailerHelper {
      * @return string
      */
     public static function pgp_encrypt(string $to, string $msg):string {
+        // Skip encryption if PGP_ENC_KEY is null
+        if (MD_CONF_EMAIL::PGP_ENC_KEY === null) {
+            return $msg;
+        }
 
         $gpg = new gnupg();
         $gpg->seterrormode(GNUPG_ERROR_EXCEPTION);