Thank You For Thank You Retiring Boss
Dear {Boss},
I know plenty of people who complain about their bosses, fortunately, that has never been the case for me.
More than a boss, you've become a friend over the past {number of} years that we've worked together. You truly cared about your {team/employees} and we're all so lucky to have had such a great leader.
Thank you for inspiring us to do our best every day. I will miss your wisdom and support.
Enjoy your retirement!
Warmly,
{Your Name}