Go to Analytics and click the Top Senders tab. This lists the email addresses (and sending domains) that have sent the most email across all your aliases, ranked by volume.
What you'll see
Each row shows the sender's address, how many emails they've sent in the selected period, and which alias or aliases they sent to.
What it's useful for
Identifying who uses your aliases most — if a sender you don't recognise is near the top of the list, it's worth investigating which alias they're reaching and whether you still need it.
Spotting high-volume marketing senders — newsletters and automated emails often dominate the top of this list. If a particular sender is sending far more than you expect, you might want to unsubscribe or deactivate the alias they use.
Checking after a breach or spam spike — if you started getting a lot of spam recently, the top senders list will show you where it's concentrated, helping you identify which alias to deactivate.
Time range
Like all analytics tabs, this reflects the selected time range. Switch to 30 or 90 days for a more complete picture of long-term sender patterns.