Is mailchuck.com working for you? It went down for me some years ago, haven't seen it since.
I recently created an account and it was working for me, but I have not paid in BTC for that account, for sending messages.
So you are not having this experience? This has been the past few years for me: $ curl -v https://mailchuck.com/ * Trying 85.25.152.9:443... * connect to 85.25.152.9 port 443 failed: Connection refused * Trying 85.114.135.102:443... * connect to 85.114.135.102 port 443 failed: Connection refused * Failed to connect to mailchuck.com port 443 after 287 ms: Connection refused * Closing connection 0 curl: (7) Failed to connect to mailchuck.com port 443 after 287 ms: Connection refused $ curl -v http://mailchuck.com/ * Trying 85.25.152.9:80... * connect to 85.25.152.9 port 80 failed: Connection refused * Trying 85.114.135.102:80... * connect to 85.114.135.102 port 80 failed: Connection refused * Failed to connect to mailchuck.com port 80 after 303 ms: Connection refused * Closing connection 0 curl: (7) Failed to connect to mailchuck.com port 80 after 303 ms: Connection refused