Sometimes it's important just to give a general thanks to excellent work so that the employees feel appreciated, that's what this email is.
Subject Line: Thank You
Dear [Title and Name of Recipient],
On behalf of [Company Name], I would like to thank you for the recent excellent work you've been doing for us. We value your commitment and your energy and we appreciate it.
Keep up the great job and greater things are ahead!
Best regards,
[Full Name]