Well done getting notes of appreciation from clients!
Please keep in mind that these testimonials are not just about you: They are about your team and your company. They are a very valuable business asset.
- For one thing they probably explain what you did that helped the client. Your team can use that information to help improve what you all do for every client.
- They also can be used, judiciously, to help your marketing and sales people strengthen the company's market position and improve sales materials.
There's probably only one other kind of note from a client that's MORE valuable, and that is a well-reasoned complaint.
So, YES, let both your outgoing and incoming manager know about these client appreciations. You, or your manager, should also inform the sales team about them.
If your managers are wise, they will decide that the new one will write a note back to the customer saying something like this: 'Thank you for letting me know how my new team member has helped you. I'm delighted to be working with this person and this team, and I invite you to contact me at any time.'