There is no such thing as free. They’ll nag you for hosting on their site. UI will degrade over time. Something will give, if not now, at some point in the future. Lifetime is a bold claim. I’m being cynical but this smells like an attempt to get a whole lotta buzz.
I also do not buy the Swiss marketing. You know how you know a company is Swiss? They’ll tell you. 100% of the time, every time.
That said, I think Swiss laws are great and immune to a lot of bullshit.
Edit: I meant free in absolute sense. There are some relatively free things out there. For example: readthedocs.org, but runs on donations from big companies like Microsoft. Same with GitHub (free private repos after Microsoft acquisition). Perhaps Ik is big enough to afford to build goodwill through free email? I know Apple is getting a lot of flak lately, but iCloud email is also “free” and not adtech driven.