
|
|
|
|---|---|---|
Open rates | Less reliable | Affected by image caching and privacy features; not directly tracked by |
Clicks | Highly reliable | Direct user interaction, indicating engagement and interest. |
Spam complaints | Highly reliable | Strong negative signal to |
Authentication (SPF, DKIM, DMARC) | Critical | Verifies sender identity, crucial for trust and avoiding spam filters. |
