Explanation/Reference:
Explanation:
An Office 365 administrator can use the Mail Protection Reports in Office 365to view data about malware, spam, and rule detections for up to the last 90 days.
The reports can be viewed as a graph to display trends for email messages over a period of time; in this question, for the last 60 days. The graph view will tell you if the amount of good mail, malware and spam detected has increased or decreased over the time period of the report.
The Received Mail report shows the received mail grouped by traffic type:
Good mail - messages that were received and not identified as spam or malware.

Spam - messages identified as spam.

Malware - messages that contained malware.

Transport rules - messages that matched at least one rule.

References:
https://technet.microsoft.com/en-us/library/dn500744(v=exchg.150).aspx