It looks like DNS is just shared CloudDNS, and email is limited. From the FAQ:

How reliable is dot.bs DNS hosting?

dot.bs is backed by ClouDNS. ClouDNS serves over two billion DNS queries per day, so I can confidently say your DNS is in good hands.

Do I really get free email?

Yes! In order to make this possible, there are some limitations. A maximum of 5 email accounts per domain (unlimited domains) A maximum of 5 outgoing emails per hour, per account (to prevent spammers) A maximum of 75 MB storage per account If these limits are a problem for you, please reach out and we can figure something out.