The short answer
A missed-call email tells the people who need to call back that a caller was lost. It is a per-line alert, not a report: one email per call, with everything in the subject line and an empty body, the same shape as the call-notify emails you may already know.
What the email looks like
From an extension: "Missed Call from 9175330756 - JOHN SMITH at Aug 20, 2026, 9:23:51 AM". From a group, queue or menu the line's own name is in it too: "Missed Call to Coordination Department from 9175330756 - JOHN SMITH at ...". It arrives within seconds of the call ending.
Turning it on
It is off on every line by default and the card is hidden until it is added. It is switched on from the line's own page in the portal: + Features, then Settings, then Missed Call Email, with the addresses separated by commas. We do this for you when you ask. A bad address is refused on save.
What counts as missed
On an extension: a call that rang that person directly and nobody picked up, including a caller who then left a voicemail. It does not email while the extension is forwarded, because whoever the call moved on to owns it.
On a hunt group, call center or auto attendant: a call that reached it and that nobody answered, whether the caller hung up while it rang, every member rang out, or the caller ended in voicemail. It does not email when the group handed the caller on to another menu or queue, and it does not email when somebody picked the caller up later in the same call.
It never emails for outgoing calls, internal calls, or answered calls.
Why the email and the Missed tile can disagree
The Missed tile on a group's Overview tab counts only callers who hung up; callers who ended in voicemail are counted there as Diverted. The email deliberately counts both. The tile answers how the group is performing; the email answers who needs calling back. For totals and a list to work through, use the Unreturned tile in Reports. See reading a call journey, and missed calls.
If the emails stop
Alerts that worked and then stopped on one day, with nothing changed, are a block on the address after a bounce. See notification emails stopped arriving.