The Quarantine Plus feature enables you to view and, optionally, re-queue messages that failed to deliver to your mail server:
To view failed deliveries:
1) Go to the Quarantine+
tab in the SpamHero control panel.
2) In the Message Search & Filter
box, click on the Show clean messages
option and then select Failed deliveries
from the drop-down list, as shown here:
3) Click on the Apply filter
button to see the messages that are waiting to be delivered.
4) Use the view delivery logs
option to view the logs for individual messages and determine why the delivery failed:
5) After resolving the issue, you can click on the re-deliver message
link of individual messages or re-queue all failed deliveries by clicking on the bulk redeliver
feature. It is recommended that you confirm the problem is resolved by re-queuing a single message before using the bulk redeliver feature: