fix message for more than one recipient

Signed-off-by: Florian Brandes <florian.brandes@posteo.de>

smtprd_ng/smtprd.py

@@ -316,13 +316,18 @@ class SMTPClient(SMTP):
                 f"'{message.get('Subject', '')}'"
             )
             if self._config.smime_cert and self._emails.email_certs[recipient] != "":
-                message = self._encrypt_and_sign(message, recipient)
+                m = self._encrypt_and_sign(message, recipient)
+            else:
+                m = message
+                m.add_header("From", self._config.sender)
+                m.add_header("To", recipient)
+                m = m.as_bytes()
             async with (
                 self._lock
             ):  # TODO: consumer task from spool queue, reusing connections
                 try:
                     await self.connect()
-                    await self._send_message(message, self._config.sender, recipient)
+                    await self._send_message(m, self._config.sender, recipient)
                 except SMTPRecipientsRefused as e:
                     raise RuntimeError(
                         f"Recipients refused: {', '.join(_.recipient for _ in e.recipients)}"