Contrary to the quarantine -which is meant to help in exploring each blocked message- the communication logs are best used for specific diagnosis. Because of the impressive number of entries, the logs aren't meant to be monitored line by line.

The Communication Logs can be found under:
My Organization → Logs

Information Display

Date and time
Date/time of message reception
From Sender's email address
To Recipient's email address
IP address
IP address of the sending server (the server that relayed the message to our filters)
Filtering Whether email filtering considered the message  Accepted or Blocked
Delivery Whether our filters were able to relay the message to your server. Statuses are  DeliveredFailed or Ongoing
View A link that allows the user to consult the log excerpt to gather more information

Searching the logs

The logs can only be searched for one destination domain at a time (found in the Domain field). By default, the search period is for the last 24 hours. Log searches can't be done farther than 30 days in the past. There is an approximate 30-second delay between a message being filtered and it showing up in our communication logs.
A default search will return results for all senders and all recipients. Due to the impressive volume of filtered emails, we recommend that searches be narrowed using sender and/or recipient information.

Understanding Search Results

Here are some things to keep in mind when viewing your log search results:
  • If there are no results, it could be because the search terms are incorrect. 
    • Remember to search using the SMTP-From and SMTP-To address. 
    • If a date/time was specified, maybe widen the search window. 
    • If you have multiple domains, make sure you're searching the logs for the correct domain.
  • If, having re-checked your search terms, there are still no results, it may be that the message never reached our filters.
  • When viewing the search results, the Filtering and Delivery columns give a brief overview of what happened with the message. 
    • For more details, click the View link. This will give you more detailed information (eg.: bounce message, your server's SMTP confirmation, the temporary SMTP error returned by your server, etc).