I have learned, much more than once, that if you have bad news for work customers, make a phone call! If you don’t reach you person, just keep playing phone tag until you connect.
An email just has way too much potential to be misinterpreted, forwarded, both.
You might think it’s the other way around (I did!), but with a call you get to hear the questions and concerns, and address them on the spot.
I am also learning not to kick myself (for very long) when I get it wrong and have to learn something again (and again).