Transport headers are empty for messages from outlook2019

Hi,

I experienced that older emails (probably from outlook 2010) are still working. For newer emails from
2019 (eventually also from outlook 2016) the headers are empty.

```json
[
    headers: TransportHeaders {
        content_type: "",
        date: "",
        message_id: "",
        reply_to: "",
    },
]
```

Any ideas / suggestions? Thanks!!