Dear {Employer/Colleague/Staff},

Wow! I still can't get over the super fun retirement party you all threw for me {yesterday/the other day}. What a way to mark the end of a chapter—you guys are truly the best!

Thank you from the bottom of my heart. Not just for the party and gifts, but more importantly for the wonderful {number of} years we spent working together. As much as I loved my job, coming in to {company} every day was made more enjoyable because of the people I worked with. So, thank you.

I'll miss {recipient's positive qualities or memorable moments}. I'm sure we'll still see each other outside of the office every now and then. You know where to reach me!

Best,
{Your Name}