What is the purpose of the spam by sender report

[VladaFBiH]

Related to this question that was never answered: Clarification about Local Spam by Sender report - Fortinet Community
What does the Spam by Sender report signify?

Are the listed accounts sending spam or recieving it?

The report says that in the last 24h one account has 4 Spam by Sender events. Looking at the logs for this account I can see that it has "sent" a bunch (20 to 30) of incorrect SMTP authorization requests which were rejected, this is normal and one accepted email sent.

Looking at the received emails 4 were received but none of them were marked as spam they were all accepted.

So what does the Spam by Sender signify?

[AEK]

Spam by Sender report lists top spammers (who send more spams).

When you see the content of the 4 accepted mails, are they actually spam or not?

[VladaFBiH]

All of them are marketing for different things so I can understand if that qualifies as spam.

But these are emails that arrived TO that users address so its users that GET the most spam?