How to send 0.0000004 BTC?
Tell me please if there are any services that allow sending such small amounts?
Before people answer you, I think you should tell us why you are sending such a ridiculously low amount (≈$0.044).
40 satoshi? I'd use the lightning network for that. But then if you don't already have them in the lightning network, you would need to pay more to convert them to LN.
Either way, this is ridiculous, unless he is trying to create his own service that will be able to achieve that. I've not seen a service going that low. But if there is any willingness to do that, especially the Lightning Network, what about the larger amount that will be paid to push it through? I see this as a joke, to be honest, it doesn't make any sense from every angle.