It seems to be working fine. I think 6 hours is too few, I'll increase it to 12 and see if it becomes less noisy.
Let's increase it to 12 hours: https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/merge_requests/50
Quoting alertmanager@hetzner-nbg1-02.torproject.org (2024-09-16 07:14:45)
Total firing alerts: 1 Total resolved alerts: 0
## Firing Alerts
Time: 2024-09-16 05:14:14.934 +0000 UTC Summary: There might be a problem with the email delivery Description: No email has arrived to gettor for the last 6 hours
##Resolved Alerts