---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/50421#article
headline: "50421: Invalid last read message index format"
url: https://www.twilio.com/docs/api/errors/50421
inLanguage: en
dateModified: 2026-03-11T20:43:38.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 50421: Invalid last read message index format

Log Type: APPLICATION

Log Level: ERROR

## Description

Request does not contain correctly formatted parameter for last read message index

### Possible causes

Request does not contain correctly formatted parameter for last read message index

### Possible solutions

Confirm a valid parameter is passed in request.