Horrific bug: Apple Mail sends 6 copies of scheduled email under embarrassing circumstances

Horrific bug in Apple Mail's "Send Later" feature: scheduled email may be sent as many as 6 consecutive times.

I made my tenants an offer to renew their lease. I scheduled a follow-up email. Didn't hear back from them. Later happened to log into Gmail's web interface, and was mortified to find that my scheduled email was sent 6 consecutive times over the course of the morning.

Such a bug might have under different circumstances been no big deal. But because my email was a follow-up about their pending renewal, I appeared as a maniac pressuring them to sign.

After explaining the situation, my tenants appear to mostly believe me. But our relationship took some damage from the incident. It was a professional embarrassment for me.

MacBook Pro, 13-inch, M2, 2022, 8GB RAM

macOS Sequoia v15.0.1

Apple Mail v16.0 (3818.100.11.1.3)

I apologize for including no reproduction steps. As far as I remember, I used the "Send Later" feature "normally." That is, I clicked the dropdown arrow, scheduled my send; and I don't recall noticing any abnormalities at the time.