Incident in progress
EmailSubject: [Product] is partly down: what we know so far
Hi [Customer name],
Since [time and timezone], [what is broken, in plain terms: some customers can't log in, emails are delayed]. Your data is [safe / not affected], and [what still works].
Our engineers are working on it now. We don't have a confirmed fix time yet.
We'll post the next update on [status page link] by [time], and sooner if anything changes. You don't need to reply to this message for us to know you're affected.
[Agent name]