I played around the rules and entered some random characters during registration process, so I managed to test register even with fake email containing only @ character with two letters, one before and one after.
This is probably not great for security, but since this is acting as a salt you can just type longer random passphrase containing one @ character.
I don't like that you are using some new stablecoin connected with USDT token on ethereum blockchain, and I don't understand how this exactly work.
Can you please explain to me how this exchange can be called decentralized when it's available on only as web version and it's operated by centralized server?
If someone attacks or shuts down the server, what happens with exchange?
There is already decentralized exchange for Bitcoin called Bisq, but you need to download and sync software on your computer.
I think it's important to post your github page, so that anyone can check the code:
https://github.com/bitcoin-dex/bitcoin-dex