- Level
- confirmed
- Worst impact
- Degraded
- Components
- Message Sending
- Down Index
- 20of 100
What to do
Check whether you use Customer.io Message Sending. Check your stack
Paste a package.json, lockfile, Terraform or a list of domains at down.guide/stack to see every provider you depend on.Confirm your retries, queues and scheduled jobs caught up after the 1h 19m it lasted.
Anything that failed between 2026-09-04 12:16 UTC and 2026-09-04 13:35 UTC may need a replay.Subscribe to Customer.io's feed to hear about the next one first. RSS feed
https://down.guide/feed?provider=customerio works in Slack (/feed subscribe), Discord feed bots and any RSS reader.
Updates from Customer.io 3
- 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!
provider
- 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.
provider
- 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.
provider
Reports count in aggregate; nothing about you is shown.
Corrections
None so far.
Something wrong on this page? Report an error or send us a note. Every fix is listed here.
Questions about DWN-1ca6244164
Is Customer.io still down?
No, this incident was resolved 2026-09-04 13:35 UTC. For Customer.io's live state, see https://down.guide/customerio.
How long did it last?
1h 19m, from 2026-09-04 12:16 UTC to 2026-09-04 13:35 UTC, by the times Customer.io posted.
What was affected?
Customer.io named Message Sending.
What caused it?
Customer.io hasn't published a root cause. If it does, it shows here.
Where does this come from?
Customer.io's official status page, https://status.customerio.com, quoted verbatim. down.guide's own probes, reports and social counts are labeled as ours.