Bad news in the first line

A slipped deadline or a cancelled plan that somebody will be unhappy about.

This is bad news. Put it in the first line, say what it means for them specifically, and give the next concrete date even if that date is only when they will hear more. No preamble, no apology longer than a sentence, nothing about being excited.

Situation:

Hard news and conflict. Bad news, apologies, angry replies, boundaries and feedback that has to survive in writing.