If you are wondering about jurisdiction, according to their FAQ they are in Switzerland, and according to geoip their servers are hosted by OVH in France.
Hm, I'm rather surprised by the fact they are hosting mail servers with OVH. Most OVH servers are on several blacklists and OVH do not tend to take very kindly to people using email through their servers.
This is a relevant question to me as well. Where the servers and backups are hosted is important.
Their web server or the actual email servers?
Strangely, both seem to use the same IP addresses (Maybe there is a load balancer there?) So, as far as I know, both are in France.