Email Technical Guidelines & Notes

Email Validation

This new email syntax validation process is an enhancement to Braze’s existing email syntax validation process. Email validation is done when a user’s email address has been updated or is being imported into Braze via API, CSV Upload, or modified in the dashboard. This validation is not to be confused with a validation service like Briteverify. This is a check to verify that the syntax of an email address is correct (for example: has an @ symbol). One of the main drivers to use this new validation process is to provide support for international characters (i.e. UTF-8) in the local part of the email address.

Email Syntax Validation looks at both the Local and Host part of an email address. The local part is anything before the @ symbol, and the host part is anything after the @ symbol. Note that this process is only validating the syntax of the email address, and does not take into account whether the domain has a valid MX server or if the user exists on the domain listed.

Note: If the domain part contains any non-ASCII characters, it will need to be punycode-encoded before being supplied to Braze

If Braze receives a request to add a user and the email address is considered invalid, you would see an error response in the API. When uploading via CSV, a user would be created, but the email address would not be added.

Local Part Validation Rules

Microsoft Domains

If the host domain includes “msn, hotmail, outlook, or live”, then the following regex will be used to validate the local part:


The microsoft address local part must follow these parameters:

  • Can start with a character (a-z), an underscore (_), or a number (0-9).
  • Can contain any alphanumeric character (a-z or 0-9) or an underscore (_)
  • Can contain the following characters (.) or (-)
  • Can not start with a period (.) or hyphen (-)
  • Can not contain two or more consecutive periods (.)
  • Can not end with a period (.)

All Other Domains

For all other domains, Braze allows email addresses matching the following regex for the local part:


The local part must follow these parameters:

  • Can contain any letter, number or underscore, including Unicode letters and numbers
  • Can contain but may not start or end with the following characters: (.) (+) or (')
  • Can contain and end with, but may not start with the following character: (-)

Host Part Validation Rules

IPv4 or IPv6 addresses are not allowed in the host part of an email address. Also, the top-level domain (e.g. .com, .org, .net, etc.) may not be fully numeric.

The following regex is used to validate the domain:


The domain must follow these parameters:

  • Consists of two or more period-separated parts.
  • Must contain at least one period (.)
  • Cannot contain two or more consecutive periods
  • Each period-separated part must:
    • Start with an alphanumeric character (a-z or 0-9)
    • End with an alphanumeric character (a-z or 0-9)
    • Only contain alphanumeric character (a-z or 0-9) and the hyphen (-)
    • Contain from 1 to 63 characters

Additional validation required

  • The final part of the domain must be a valid top-level domain (TLD) which is determined by anything after the final period (.)
  • The TLD should be in ICANN’s TLD list.
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