Hi Wong Yeong Ru thanks for reaching out. This could be a case of the student's email provider are blocking emails coming from *@openlearning.com as well as from @amazonses.com (we use this for some automated emails such as password resets).

For us to check on this further, could you please email us at support@openlearning.com the student's email addresses so we could check?

We look forward to your email. Thank you.