Here’s an email you can send to a coworker on his first day of joining your team:
Hey [Name],
Welcome to the team!
We know you'll be a terrific addition, and we wouldn't have recruited you if we didn't think that.
We look forward to helping you on your journey.
Congratulations on your new job, and best wishes for a successful first day at [business name].
Regards,
[Your name]