Had a chance to analyze several Google Postmaster graphs and noticed sudden spikes in spam report complaints on days with almost no email traffic, including the preceding week.

In one instance, we observed a 33% spam report rate, even though the domain sent fewer than 150 emails that week.

In another scenario, there was a 50% spam report rate, while the email traffic in July did not exceed 250 emails per day and was used solely for 1-1 communication via Gmail.

In both cases, we compared the Google Postmaster graphs with the DMARC reports for the corresponding periods.

My personal conclusion is that Google Postmaster continues to face challenges in accurately reflecting domain-related information.