Which metric is most closely aligned with deliverability health?

• A. Revenue per subscriber
• B. Unsubscribe rate
• C. Deliverability health indicators such as bounce rate and spam complaints
• D. Social shares

Answer: (C)

Deliverability health is measured by signals that reflect whether your emails actually land in inboxes or get blocked or marked as junk. The most direct indicators are bounce rate and spam complaints because they show how ISPs and mailbox providers are treating your messages. A high bounce rate signals bad list hygiene or invalid addresses, which harms sender reputation and can block future deliveries. Spam complaints tell providers that recipients don’t want your messages, leading to filters that push your emails further down or out of the inbox. Together, these indicators reveal the true health of your deliverability and guide you to clean lists and improve permission practices.

Other metrics like revenue per subscriber, unsubscribe rate, or social shares gauge engagement or monetization, not the inbox delivery path itself, so they’re not as closely tied to deliverability health.