Article blue links need testing?
The article at fitsmallbusiness.com/free-business-email-address/ indicates you can check if your desired domain is available, but test those blue links and they all end up dropping you into a sales screen (some of which say “on sale for $11.xx for $1/1st yr then $19/2nd.!)
As it indicates in the article, you will be taken straight to the registration page if the domain name is available. If it’s not, you’ll get a message that says it’s not available for registration.
Sounds like you were taken to the checkout page which means the domain you entered is available!