They want you to stop using the word "smartcontract" - there's a live (but likely unenforceable trademark) here:
https://tmsearch.uspto.gov/bin/showfield?f=doc&state=4809:kjt3d4.2.1Also from what I can gather you'd have to be:
1. Located in the US for this to be enforced
2. Be conducting a similar type of business to what the trademark owner is doing (and I don't think that's been established anywhere what they're doing or what the issue is).
In a lot of countries, with trademarks, you normally have to prove people have misrepresented the company by using it and have caused them losses as a result but I'm not sure this is the case in the US.
Being funnily pedantic, have you written that term without a space on your website (only look if it's a quick search)?