Brevo marks an SMTP key inactive after three months without a send. That key is a\nseparate credential from the REST API key, used only by Cloudflare Email Routing in\nBrevo re-send mode. Low-traffic role addresses can go three months without a single\nmessage, so the key expires purely from disuse while the routing rule is still enabled.
\nWhen that happens the failure is not graceful: the relay fails, Cloudflare rejects the\nmessage, and anyone emailing that role address gets a bounce. Nothing in the admin UI\nwarns beforehand.
\nAdds a monthly keepalive task that sends one probe through the same relay the inbound\nrouting uses, which resets the inactivity clock and doubles as an end-to-end check. It\nappears in Scheduled Tasks with run history, an enable toggle, an editable schedule and\na manual trigger, so a failure shows up there rather than as a bounce to a member. The\nprobe recipient is configurable in Mail Settings and falls back to the SMTP login, and\nthe task skips itself on sites that do not use Brevo re-send.
\nScheduling it monthly exposed a defect in overdue detection, fixed here too. The\nwatchdog treated any day-of-month schedule as a flat 28 days, which for a monthly task\npointed the previous expected run a few days after the run that actually happened, so it\nwould raise a missed-run alert and re-run the task every month. Overdue detection now\nworks out the true previous occurrence from the schedule itself. Checked against all\nseven existing schedules: only the monthly one moves, to the correct date, and genuine\nmissed-run recovery still works.
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