Determining a safe email delivery rate threshold is complex and multifaceted. While aiming for a delivery rate above 90-95% is often suggested, it is crucial to understand that this is only one piece of the puzzle. Experts and marketers emphasize the importance of monitoring various factors, including sender reputation, authentication (SPF, DKIM, DMARC), list hygiene (regularly cleaning and validating lists), bounce rates (hard bounces below 2-3%, with an ideal target of below 0.5%), spam complaints (below 0.1%), inbox placement, and engagement metrics (opens, clicks). Furthermore, relying solely on the delivery rate can be misleading, particularly with Gmail-heavy lists where spam complaint rates can be skewed. Other considerations include defining metrics for your organization, reviewing bounce error logs, and understanding the impact of business strategy and international opt-in laws. It's important to avoid spam traps, monitor trends specific to your sending profile, and ensure that your email validation is up-to-date. Ultimately, focus on creating a healthy sending ecosystem with high engagement, positive sender reputation, and consistent adherence to best practices.