We don't allow a way to send encrypted email directly, because the intersection between people who wanted it and the people who would trust us with their private keys was too small to be worth it. Instead, we provide standard protocols (IMAP/POP/SMTP) so you can run the crypto software on your own computer and submit and receive through us. This gives you full encryption support.
We're probably similar in security to gmail - they're very good as well - most of the big services are. The main comparison at that level is the unpatched server running in the basement of a business somewhere - or indeed the "roll your own" where it gets updated once every few months if the person running it remembers and isn't on holiday at the time... it's nice having a team and always someone on duty for security.
Ok - I initially misunderstood that you were saying FastMail does the same thing as Tutanota. When I reread your comment I see that you aren't saying that - just that you secure transit with TLS, etc.
We're probably similar in security to gmail - they're very good as well - most of the big services are. The main comparison at that level is the unpatched server running in the basement of a business somewhere - or indeed the "roll your own" where it gets updated once every few months if the person running it remembers and isn't on holiday at the time... it's nice having a team and always someone on duty for security.