---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/glossary/unknown-user#article
headline: Unknown User
description: "*Email Deliverability*. The removal of recipient email address that doesn't exist on the recipient email server from a contact list."
url: https://www.twilio.com/docs/glossary/unknown-user
inLanguage: en
dateModified: 2026-07-20T14:57:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Unknown User

*Email Deliverability*. The removal of recipient email address that doesn't exist on the recipient email server from a contact list.

This error displays as `Bounced - Unknown User`. It indicates the email address doesn't exist and you receive `Unknown User` response.

## Related entries

* [Bounces](/docs/glossary/bounces/)
* [Subscriber List Management](/docs/glossary/subscriber-list-management/)