The email specified in the "to"-field is semi-silently ignored if the email doesn't exist.

POST body:
```json
{
    "to": "....",
    "from": "your_lord_and_saviour@chalmers.it",
    "subject": "....",
    "body": "...."
}
```

Response:
```json
{
    "to": "....",
    "from": "admin@chalmers.it",
    "subject": "....",
    "body": "...."
}
```

Perhaps this should be an error instead?