How to stop an email sending based on submitted values

If you need to stop email notifications based on a submitted field value, you may use the af/form/email/recipient filter to override the recipient list based on the form's configuration args. A return value of FALSE will disable the notification email.

<?php

function conditionally_send_email( $recipient, $email, $form, $fields ) {
  // Check for correct form.
  if ( $form['key'] !== 'FORM_KEY' ) {
    return $recipient;
  }

  // If submitted field value doesn't match the expected value, return FALSE to stop email sending.
  if ( af_get_field( 'my_field_name' ) !== 'some value' ) {
    return FALSE;
  }

  return $recipient;
}

add_filter( 'af/form/email/recipient', 'conditionally_send_email', 10, 4 );