It is possible. Presently we are expected to support the following custody options:

1. Use @finmail.com as main domain to handle both email and digital currency. All domain, mailbox and coin wallets are hosted by us, like the Finmail Mailbox.
2. Use custom domain from users. Domain is self-custody by users, while mailbox and coin wallets are hosted by us.
3. All domain, mailbox and coin wallets are self-custody by users.

All transfers of BTC/USDT can be made by email address. Within the same hosts, they goes through internal transfer, while between different hosts they goes through external transfer, i.e. BTC/USDT network.

Users can also send/receive just coins by email addresses, if they do not plan to use mailbox. In this case, there is no need to host mailbox.

All 3 options have been realized through our internal test. However, since option 3 needs to release source code to users, for security purpose, it may not be available at the moment. We may release options 3 when appropriate.

If interested, you are welcome to try option 1 and 2. To option 2, please contact us for more details.