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Invalid Email


Occurs when sending message to an email address doesn't follow the Internet Engineering Task Force (IETF)(link takes you to an external page) email address syntax standards.

Twilio retains reports of invalid email addresses for 30 days.


Email syntax

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The IETF set the syntax for email addresses in three Requests for Comment (RFC): RFC 3696, RFC 5321, and RFC 5322.

These RFCs consider an email address invalid when it fails to meet any of the following conditions:

Length of email addresses

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These RFCs define length in octets rather than characters.

  • A single character in a non-Latin alphabet may use more than one octet, or eight bits, of data.
    For example: the local-part of an email address using Chinese characters can't exceed 32 characters.
  • [RFC 6531][rfc-6531] covers Unicode characters in the local-part of an email address.
    This requires the SMTPUTF8 extension(link takes you to an external page) for your email provider.
  • [RFC 5890][rfc-5890] covers Unicode characters in the domain part of an email address.
  • Support for international characters depends on the email provider.

Valid characters for email addresses

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  • The email address doesn't include the @ symbol between the local-part and domain part.
  • The local-part of an email address includes characters other than the following:
    • Letters (A-Z, a-z).
    • Digits (0-9).
    • Special characters (!, #, $, %, &, ', *, +, -, /, =, ?, ^, _, `, {, |, }, ~, .).
  • The local-part starts with a period (.) or includes two or more periods in a sequence (first..last@example.com).