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CompaniesCustomer.ioIncidents

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

No impact listedStatus: resolvedStarted Resolved (0 min)3 updatesstatus.customerio.com (opens in new tab)

Affected components: Message Sending

Timeline of updates

  1. investigating

    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!

  2. monitoring

    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.

  3. resolved

    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.

Archive proof

Rewindex commits each version of an incident it captures to a daily checkpoint, chains it to the day before, and has the checkpoint timestamped by FreeTSA and DigiCert. That proves this record existed by then and has not been changed since, by anyone, Rewindex included.

How the archive is checked, and what it cannot prove.

Impact, status and times are the vendor’s own, as last archived. View on status.customerio.com (opens in new tab).

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).

Title
Reduced Deliverability to Microsoft-Hosted Email Addresses
Vendor
Customer.io
Date
URL
https://rewindex.com/company/customer-io/incidents/7zy2yljd0z5r

Customer.io profileRecent Customer.io incidentsAll outages on September 4, 2026Customer.io in September 2026MarkdownJSON