The mailfy program attempts to use pgp.key-server.io that has long since been deprecated and is no longer accessible returning an error:

MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='pgp.key-server.io', port=443): Max retries exceeded with url: /pks/lookup?search=amir.hassanali@libero.it (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f008e977a10>: Failed to establish a new connection: [Errno -2] Name or service not known'))