# Customer.io: Reduced Deliverability to Microsoft-Hosted Email Addresses

> Customer.io status incident “Reduced Deliverability to Microsoft-Hosted Email Addresses” on 2026-09-04: impact none (vendor’s label), 0 min, 3 update(s). Archived by Rewindex.

Canonical: https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r
Last updated: 2026-09-04T13:35:47Z

- Impact (vendor’s label): none
- Status: resolved
- Started: 2026-09-04 13:35 UTC · Resolved: 2026-09-04 13:35 UTC · Duration: 0 min
- Updates: 3 · Affected components: Message Sending
- [Vendor status page: https://status.customerio.com/incidents/7zy2yljd0z5r](https://status.customerio.com/incidents/7zy2yljd0z5r)
- [Company: Customer.io](https://rewindex.com/company/customer-io.md)

## Timeline of updates

- **investigating** 2026-09-04 12:16 UTC: We are currently investigating reports of reduced deliverability affecting messages sent to Microsoft-hosted email addresses. Our team is actively looking into this and we will provide an update as soon as we have more information. Thank you for your patience!
- **monitoring** 2026-09-04 12:30 UTC: Starting around 08:00 UTC, Microsoft began experiencing an incident causing an increased volume of deferred/bounced emails. We are actively monitoring the situation. No other email providers are currently affected.
- **resolved** 2026-09-04 13:35 UTC: Microsoft has resolved the underlying issue, we are seeing deliveries to their services resume as normal. Earlier bounces will be retried accordingly. We appreciate your understanding and please do reach out to support if you need any further assistance.

## Cite this

Status incident (vendor impact label: none) posted by Customer.io, started 2026-09-04 13:35 UTC, resolved after 0 min, 3 update(s).

- Canonical URL: https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r
- Citation: Customer.io, “Reduced Deliverability to Microsoft-Hosted Email Addresses” (2026-09-04 13:35 UTC). Archived by Rewindex: https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r (CC BY 4.0).
- Markdown link: `[Customer.io: Reduced Deliverability to Microsoft-Hosted Email Addresses (2026-09-04)](https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r)`


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Canonical: https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r · Markdown: https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r.md · JSON: https://rewindex.com/api/v1/companies/customer-io/incidents/7zy2yljd0z5r · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-04T15:05:09.014Z