Kindly for "K"

Be kind to others. Be considerate of your readers.

So when you write, take care to include all the dates, facts, and figures that the person may need to handle your query or request or instruction.

In business letters, include everybody's file reference numbers if you have them.

Give a quick summary of a letter or request that you are responding to.

Just don't force the other person to go searching for their file, records, or catalogue in order to deal with your letter.

The selfish benefit of this is that you are more likely to get an early response if you save your correspondent the time to sort this all out.