wp_send_user_request( string $request_id )

function wp_send_user_request( $request_id ) {
	$request_id = absint( $request_id );
	$request    = wp_get_user_request_data( $request_id );

	if ( ! $request ) {
		return new WP_Error( 'user_request_error', __( 'Invalid request.' ) );
	}

	$email_data = array(
		'request'     => $request,
		'email'       => $request->email,
		'description' => wp_user_request_action_description( $request->action_name ),
		'confirm_url' => add_query_arg( array(
			'action'      => 'confirmaction',
			'request_id'  => $request_id,
			'confirm_key' => wp_generate_user_request_key( $request_id ),
		), wp_login_url() ),
		'sitename'    => wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ),
		'siteurl'     => home_url(),
	);

	/* translators: Do not translate DESCRIPTION, CONFIRM_URL, SITENAME, SITEURL: those are placeholders. */
	$email_text = __(
		'Hello,

A request has been made to perform the following action on your account:

     ###DESCRIPTION###

To confirm this, please click on the following link:
###CONFIRM_URL###

You can safely ignore and delete this email if you do not want to
take this action.

Regards,
All at ###SITENAME###
###SITEURL###'
	);

	/**
	 * Filters the text of the email sent when an account action is attempted.
	 *
	 * The following strings have a special meaning and will get replaced dynamically:
	 *
	 * ###DESCRIPTION### Description of the action being performed so the user knows what the email is for.
	 * ###CONFIRM_URL### The link to click on to confirm the account action.
	 * ###SITENAME###    The name of the site.
	 * ###SITEURL###     The URL to the site.
	 *
	 * @since WP-4.9.6
	 *
	 * @param string $email_text Text in the email.
	 * @param array  $email_data {
	 *     Data relating to the account action email.
	 *
	 *     @type WP_User_Request $request     User request object.
	 *     @type string          $email       The email address this is being sent to.
	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
	 *     @type string          $confirm_url The link to click on to confirm the account action.
	 *     @type string          $sitename    The site name sending the mail.
	 *     @type string          $siteurl     The site URL sending the mail.
	 * }
	 */
	$content = apply_filters( 'user_request_action_email_content', $email_text, $email_data );

	$content = str_replace( '###DESCRIPTION###', $email_data['description'], $content );
	$content = str_replace( '###CONFIRM_URL###', esc_url_raw( $email_data['confirm_url'] ), $content );
	$content = str_replace( '###EMAIL###', $email_data['email'], $content );
	$content = str_replace( '###SITENAME###', $email_data['sitename'], $content );
	$content = str_replace( '###SITEURL###', esc_url_raw( $email_data['siteurl'] ), $content );

	/* translators: Privacy data request subject. 1: Site name, 2: Name of the action */
	$subject = sprintf( __( '[%1$s] Confirm Action: %2$s' ), $email_data['sitename'], $email_data['description'] );

	/**
	 * Filters the subject of the email sent when an account action is attempted.
	 *
	 * @since WP-4.9.6
	 *
	 * @param string $subject    The email subject.
	 * @param string $sitename   The name of the site.
	 * @param array  $email_data {
	 *     Data relating to the account action email.
	 *
	 *     @type WP_User_Request $request     User request object.
	 *     @type string          $email       The email address this is being sent to.
	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
	 *     @type string          $confirm_url The link to click on to confirm the account action.
	 *     @type string          $sitename    The site name sending the mail.
	 *     @type string          $siteurl     The site URL sending the mail.
	 * }
	 */
	$subject = apply_filters( 'user_request_action_email_subject', $subject, $email_data['sitename'], $email_data );

	return wp_mail( $email_data['email'], $subject, $content );
}