To clarify and to add onto what masnick wrote, the article _was_ right. The free tier was an option previously, but FastMail has recently dropped that tier in favor of a free trial and, I'm assuming, a lower tier that has a lower cost.

Any previous users of the free tier will still have their account for free, possibly until further notice, but there is no obvious indication that they'll just drop your free account (unless you're inactive for their specified time period).

I have two email accounts with Fastmail mostly because they were the only free email service that supported Yubikey, but aside from that feature, I would call them "just another email service."