Companies/Loops/Incidents

Loops: Transactional email, webhooks, SMTP interruptions

flowchart LR
  root["AWS us-east-1<br/>posted 07:11 UTC"]:::root
  before["Posted before AWS did<br/>5 vendors, 4 blamed AWS<br/>Salesforce, Descope, Ashby +2"]:::blames
  root --> before
  h1["Within an hour<br/>18 vendors, 17 blamed AWS<br/>Asana, Firebolt, Monday.com +15"]:::blames
  root --> h1
  h4["1 to 4 hours later<br/>30 vendors, 29 blamed AWS<br/>SingleStore, Loops, Buildkite +27"]:::blames
  root --> h4
  later["Later<br/>45 vendors, 44 blamed AWS<br/>RudderStack, Airbyte, Unbounce +42"]:::blames
  root --> later
  p0["Twilio<br/>posted +15 min"]:::blames
  root --> p0
  k0["BigCommerce<br/>+2 h 46 min"]:::hop2
  p0 -->|"blamed Twilio"| k0
  p1["Webflow<br/>posted +4 h 37 min, did not name AWS"]:::timing
  root -.-> p1
  k1["Rootly<br/>+10 h 23 min"]:::hop2
  p1 -->|"blamed Webflow"| k1
  p2["Baseten<br/>posted +4 min"]:::blames
  root --> p2
  k2["Zed<br/>+26 h 20 min"]:::hop2
  p2 -->|"blamed Baseten"| k2
  me["Loops (this incident)<br/>posted +1 h 20 min"]:::me
  h4 --- me

Affected components: Email Sending - TransactionalTransactional

Timeline of updates

1. monitoring2025-10-20 08:30 UTC

   An issue in AWS is causing transactional emails to fail.

2. monitoring2025-10-20 09:55 UTC

   We are continuing to monitor for any further issues.

3. monitoring2025-10-20 10:46 UTC

   We are continuing to monitor for any further issues.

4. resolved2025-10-20 10:47 UTC

   This incident has been resolved.

5. postmortem2025-10-21 17:22 UTC

   On October 20 2025, Loops was impacted by AWS’s outage in the US-EAST-1 region. We observed a variety of misbehaviors during that time, some more serious than others. Overall, the impact to Loops fell within the wider window provided by AWS \(06:49 UTC to 22:53 UTC\). During the outage, we experienced temporary but notable impact to, * Transactional email sending. * Webhook delivery. * Incoming request routing to our SMTP service. **Transactional email** Between 7:02 UTC and 9:18 UTC, transactional email sending was impacted. During this window the Loops API may have accepted transactional requests but failed to send them. Impacted messages were not resent later as we do not store the raw payloads. Timeline: * 7:02 UTC: We began experiencing elevated error rates related to transactional email sending, manifesting as increasing rates of HTTP 500 responses from AWS APIs. * 9:18 UTC: AWS API error rates subside. Transactional sending returns to normal. **Webhooks** Between 9:30 UTC and 10:31 UTC webhook delivery was impacted due to the inability to provision sufficient EC2 capacity. Timeline: * 9:30 UTC: Error rates between the Loops API and our backend webhooks service rise. * 10:01 UTC: The issue is identified as insufficient capacity for the webhooks service due to EC2 provisioning scarcity. * 10:31 UTC: Error rates subside as we change our autoscaling configurations to accept a wider range of EC2 instance types and sizes. **SMTP availability** Between approximately 19:33 UTC and 21:35 UTC an incorrect DNS entry was returned in the results for the network load balancer \(NLB\) used by our SMTP service. During this window, one of three IP addresses returned by DNS responses were unable to accept connections. Attempts to connect to the incorrect IP address manifested as timeouts. Timeline: * ~19:33 UTC: An IP address returned NLB DNS requests stops accepting connections. DNS requests that select the impacted IP address fail to connect and time out. * ~21:35 UTC: The DNS for the NLB corrects itself and begins returning correct responses.

Changes Rewindex caught on this incident

• Oct 20, 2025Major incident: Transactional email, webhooks, SMTP interruptions

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

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