Warmth is often treated as something added after the message is written: an exclamation mark, an emoji or another friendly sentence. Sometimes that works. Often the more useful change is to acknowledge what the other person actually did or asked.
Compare ‘Send the file’ with ‘Thanks for checking this. Could you send the latest file?’ The second message recognizes the person’s contribution and makes the request specific. It does not need a long introduction.
Warmth can also come from reducing uncertainty. ‘I saw your message and will reply after the meeting’ may feel more considerate than a cheerful acknowledgment that leaves the next step unclear, provided you genuinely intend to follow up.
Keep the tone proportionate. A routine confirmation does not need to sound like a celebration. A difficult update should not be wrapped in excitement that contradicts its meaning.
Try this edit: remove the decorative friendliness from your draft and ask what concrete sign of attention remains. Have you acknowledged the effort, answered the actual question or explained the relevant next step? Add whichever one is missing.
A warm message can be concise. It shows that a person and a situation were considered, rather than simply making the sentence sound more enthusiastic.