Some things deserve to be said the long way — and this is one of them.
Hi [First Name],
I wanted to take a beat to say this properly, instead of letting it disappear in the middle of a busy week: thank you. Genuinely.
For the work, the trust, the way you keep showing up. For the calls I didn't have to make because you'd already handled it. For the standard you set just by being in the room. None of it goes unnoticed on my end, even when I'm not great about saying so out loud.
So — thank you. From me, on the record, in writing.