For some reason they don't charge for sending messages.
Finally, we are confident enough to invite interested users to test Keychat.
Keychat code: https://github.com/keychat-io
Keychat Android apk: https://github.com/keychat-io/keychat-app/releases
This version inevitably still has many bugs, which we will continuously fix. We will also modify any designs that are not reasonable. Thank you for helping to test this early-stage application.
For now, do not store too many sat(<200 sat, about 13 cents) in Keychat.
If you need some ecash sat to test the postage feature, please add 👇.
Discussion
If the user doesn't have ecash sat, the message will only be sent through the free relay.
Long press the message you sent and select raw data. 
У меня есть eCash. У relay.keychat стоит крестик, при просмотре через "raw data". Я использую mint https://mint.minibits.cash/Bitcoin.
Mint "8333" works, apparently you have limited the available mints for payment.
Keychat relay will support more ecash sats issued by other mints as stamps in the future.
BTW, the 8333 mint is not operated by us; it is the earliest Cashu mint, so we have been using it consistently.
is this the correct group to request? I tried yesterday but am getting decryption errors and there and only 'Sat' is replying:
npub17a6fz2j9h8kekhsahqzjr0tg5uawh9u3p4zg0mw9jz95tfq3ujxq7a7x39
Sorry for the bug. We have released a new version, please download it. We will re-add you as a friend using a different ID. Thank you for your testing.