The few times I've donated money to anything in the past decade or so, including to relatively uncontroversial recipients, I've done it by mailing cash in an en

The few times I've donated money to anything in the past decade or so, including to relatively uncontroversial recipients, I've done it by mailing cash in an envelope with no return address. That was partly to avoid cancellation, but also it was to avoid the recipient putting me on a donor list so they could keep hounding me for more. In one case the recipient became controversial after I sent the cash (earlier it had only been a little bit edgy or fringey) so I'm glad that I used that approach. Not worth getting hassled over $20.