[Home](./index.md) > [@digitalpersona/authentication](./authentication.md) > [EmailOtpAuth](./authentication.emailotpauth.md) > [sendChallenge](./authentication.emailotpauth.sendchallenge.md) ## EmailOtpAuth.sendChallenge() method Sends an e-mail challenge with a OTP code to the user's registered mobile device. Signature: ```typescript sendChallenge(user: User): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | user | User | a name of the user | Returns: `Promise` a promise to send the challenge code to the registered e-mail address. Will reject if user has no email or in case of any other error. ## Remarks The user has to have an email registered in their LADP user record in ActiveDirectory or LDS. The server will look for a first entry in a `mail` LDAP atribute of the user record.