---
title: 4001: Delivery failed | API Docs
description: Message could not be delivered.
---

Message could not be delivered. This may be due to an unreachable recipient or service disruption. This is an HTTP 500 error.

When `reason` begins with “Message delivery failed” (the full string may be “Message delivery failed. Please retry the message.”), a `message.delivered` webhook for the same message ID may still arrive later in some cases — as opposed to “Message send failed”, which is terminal. Send timeouts, which previously also surfaced as 4001, are now reported as code 4006 with the same may-still-deliver caveat stated explicitly.

## Troubleshooting

- Try sending the message again
- If the problem persists, contact support with the `trace_id` from the error response

## Related

- [Sending messages](/channel/imessage/guides/messaging/sending-messages/index.md)
- [Debugging](/channel/imessage/guides/platform/debugging/index.md)