Because Spam reports contain the email addresses and Subjects of many, many spam messages, ISPs that use content filters (which examine the text of the message) often identify the reports as spam themselves. Please check any Junk Mail or Spam folders your ISP may be keeping for your missing report. Also, ask how you can make discard-report@pobox.com a trusted sender, so future messages will bypass their spam filters.
We can also send a summary report, rather than a complete listing. While you would not be able to review your spam directly in a summary report, it would contain a direct link to the contents of that day's "report". If your ISP's spam filters are consistently picking up the full report due to content, a summary report may be the best alternative. Turn on summary reports for your account under "Summary or Full Content?".
Finally, if you would like to be able to automatically see when new spam comes in throughout the day, you can subscribe to an RSS feed of messages we discard for your account.