Email links blocked on user's end

We’ve got a user who can’t access any of the links in our emails. This is the error he gets: "This site can’t be reached. is-tracking-link-api-prod.appspot.com ’s server IP address could not be found.” He’s using the Outlook app.

Any thoughts on a setting he needs to change in his email? Or anything we could do on our end besides not tracking clicks?