---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/91307#article
headline: "91307: Could not connect to sink endpoint"
url: https://www.twilio.com/docs/api/errors/91307
inLanguage: en
dateModified: 2026-10-27T17:14:57.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 91307: Could not connect to sink endpoint

Log Type: APPLICATION

Log Level: ERROR

## Description

Twilio records this error when Event Streams cannot establish a connection to your sink endpoint.

Because the connection could not be established, no event was sent. Twilio will automatically retry delivery per retry policy.

### Possible causes

* The sink hostname could not be resolved via public DNS.
* The sink closed or reset the connection attempt because no service was listening on the designated port.
* A firewall, security group, or network access control list silently dropped Twilio's incoming connection request.
* The endpoint presented an expired, self-signed, hostname-mismatched, or incomplete SSL/TLS certificate chain.
* The sink hostname resolves to a private IP space or an unroutable endpoint that is unreachable over the public internet.

### Possible solutions

* Confirm that your sink's domain name is publicly resolvable and resolves to an accessible, public IP address.
* Ensure your target server presents a valid, unexpired SSL/TLS certificate issued by a trusted Certificate Authority (CA) that matches your configured domain name.
* Ensure your network firewalls, cloud security groups, or API gateways permit inbound traffic from Twilio's public IP ranges.
* Confirm that the protocol (https://) and port (default 443) configured in your sink setting match your receiving application's configuration.
* Run an external curl command or TLS verification check from a host outside your private network to isolate network reachability issues.

### Related errors

* [91300: Event delivery to sink failed](/docs/api/errors/91300)
* [91308: Sink endpoint did not respond in time](/docs/api/errors/91308)

#### Additional resources

* [Event Streams overview](/docs/events)
* [Sink resource](/docs/events/event-streams/sink-resource)
* [Subscription resource](/docs/events/event-streams/subscription)