---
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"@id": https://www.twilio.com/docs/api/errors/50408#article
headline: "50408: Invalid participant proxy address"
url: https://www.twilio.com/docs/api/errors/50408
inLanguage: en
dateModified: 2026-03-11T20:43:38.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 50408: Invalid participant proxy address

Log Level: ERROR

## Description

An invalid participant proxy address was supplied.

### Possible causes

* Participant MessagingBinding.ProxyAddress parameter provided with the request is not a valid conversation proxy address.

### Possible solutions

* Check that the length of MessagingBinding.ProxyAddress parameter does not exceed 256 characters.
* Ensure that MessagingBinding.ProxyAddress parameter contains an address with valid syntax (e.g. SMS phone numbers must follow [E.164 format](/docs/glossary/what-e164)).