Zoho Mail outgoing webhooks stopped delivering events to my domain from Aug 28 to Sep 1, 2026 — temporary suppression by destination domain/IP?

Zoho Mail outgoing webhooks stopped delivering events to my domain from Aug 28 to Sep 1, 2026 — temporary suppression by destination domain/IP?

Dear Zoho Mail support team,

I run an application that receives email notifications from several Zoho Mail accounts via outgoing webhooks (Settings → Developer Space → Outgoing Webhooks), with REST API polling as a backup.

What happened: between August 28 and September 1, 2026, no outgoing webhook delivered any new-email POST to my server — across all accounts, from two different Zoho organizations, all pointing to the same destination domain. On September 1, without any change on my side, deliveries resumed on their own.

Evidence my endpoint was healthy the whole time:

The verification POST (x-hook-secret handshake) did arrive whenever a webhook was created or re-saved; my server responded 200 echoing the secret and the webhook showed as Enabled. I have a successful handshake logged on August 28 at 23:07 UTC.
The URL is publicly reachable; I verified with manual POSTs during the incident (no firewall/WAF blocking).
Webhook configuration: entity Mail, condition "No conditions. All emails", limited-data option unchecked, status Enabled.
Incoming emails confirmed in the mailbox during those days, and zero event POSTs in my server logs after each handshake.
What I tried during the incident, without success: toggling the webhook off/on, deleting and recreating it (handshake arrived again, then silence), removing and re-linking the account entirely, and testing with accounts from a different organization — same result.

My questions:

Does Zoho Mail apply a temporary delivery suppression per destination URL, domain, or IP when an endpoint fails repeatedly? I suspect my server had some downtime before August 28 that triggered it.
How long does that suppression last, and why does it also affect newly created webhooks that verify successfully?
Could you check the delivery-attempt history to my domain between August 25 and September 1 to confirm this?
Is there any way to be notified when this happens? We lost real-time delivery for days with no warning, while the webhooks showed as "Enabled" in the panel.
I can provide the endpoint domain, account IDs, and exact handshake timestamps. Thank you very much.

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