Unfortunately there are multiple reasons why an email isn't received, and 99% of them cannot be researched by Jackrabbit. Some reasons are:
- The email was sorted to the recipient's Spam folder (so they don't know they received it).
- The email was automatically deleted by the recipient's own Spam rules.
- The recipient's Inbox is full and wont' accept any more emails until some are deleted.
- The recipient no longer has that email address.
- The recipient's Internet Service Provider (ISP) refused to deliver the email because the ISP thinks it is spam.
- The email address is mistyped in Jackrabbit (you can check this in your database).
To verify that an email was sent, you can go the Family Misc tab and click the View Sent Emails button. A popup will appear with the details of emails sent in the last 180 days to that family, including the Status. A Status of Complete means that the email was successfully sent out by the Jackrabbit server. It doesn't explicitly mean the email was received.
Additional recommendations for improving deliverability can be found in our Best Practice article Email - Improve deliverability.