This may be because your email provider (e.g.: Outlook) categorised the email as spam or junk mail. Check the contents of your spam or junk folder to see if the email is there.
If your using Microsoft Outlook and find the email in your Junk E-mail folder simply right click on the email message and choose the "Add sender to safe senders list" option. This will make sure no more emails from us are marked as spam.
For instructions for other email programs, please contact your local support function or the email program vendor.