Multiple sources, including email marketers, experts, and Google's documentation, indicate that delays and discrepancies are common in Google Postmaster Tools data. The delays stem from a combination of factors: Google's internal processing load, data aggregation algorithms, system maintenance, and potential changes in spam filtering. Sender-specific factors such as authentication, sending volume, and sender reputation also play a significant role. The tool is best used to identify trends over time rather than relying on specific daily data. Google Postmaster Tools only shows historical data so doesn't reflect real-time conditions or predict future outcomes and thus should be seen as an indicator. Discrepancies and delays could indicate deliverability issues, making it essential to audit email authentication settings and monitor sender reputation. Finally, as a free tool, its reliability and availability cannot be guaranteed.