How long should a appreciation message be?

Short and unhedged. Why now, what they did, what it meant. No request attached.

When should you send a appreciation message?

The absence of an occasion is the point. Do not apologise for the randomness of it.

Appreciation

Appreciation with no occasion attached is the rarest kind of message and, by a distance, the most affecting, because nothing prompted it.

A card on a birthday is expected. A card in the middle of March is evidence.

Say why now. "I was thinking about this and wanted to tell you" is the whole frame and it works.

Name the specific thing and the effect it had. Appreciation without evidence sounds like flattery.

Expect it to be received with some awkwardness. That is not a sign it was unwelcome.

Who you are writing to changes the message more than the occasion does. Each page below is written for one relationship.

The absence of an occasion is the point. Do not apologise for the randomness of it.
This is the right form for gratitude that has been owed for years and never delivered.
It requires nothing in return and should say so implicitly by not asking anything.

What should you write in a appreciation message?: Say why now. "I was thinking about this and wanted to tell you" is the whole frame and it works. Name the specific thing and the effect it had. Appreciation without evidence sounds like flattery.
How long should a appreciation message be?: Short and unhedged. Why now, what they did, what it meant. No request attached.
When should you send a appreciation message?: The absence of an occasion is the point. Do not apologise for the randomness of it.

Say it as something they open

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