There's also https://mykolab.com hosted in Switzerland. What's more: It is 100% Open Source, so you can host it yourself decentrally.

And you probably should, if you want to maximize your legal protections against governments where third-party access to your data gives the government easier access to your data.

All of these centralized services (such as the one you linked) are susceptible to the same strong-arm tactics if they're based in the US.

Nothing special about the USA. Hushmail is a Canadian company and they were strong-armed by the DEA.

Do not let some third party hold your keys, do not use some applet to decrypt your mail. This is public key encryption 101.