Level: Intermediate
Beyond authentication-specific headers, the broader structure and content of your message headers can meaningfully influence how filtering systems evaluate a message.
The From Header Should Be Consistent and Recognizable
Frequently changing the From name or address, or using a From address that doesn't clearly correspond to your actual sending domain, can undermine the trust consistent sending builds over time.
Reply-To Should Route to a Genuinely Monitored Address
A Reply-To header pointing to an unmonitored or non-existent address creates a poor recipient experience and can be treated as a legitimacy signal by some filtering systems.
Avoid Header Patterns Commonly Associated With Spam
Excessive or unusual custom headers, missing standard headers, or header formatting that deviates significantly from typical legitimate mail can all contribute to a message being flagged as suspicious.
Next step: Use the SeoWolf's Notepad to document your standard header structure and formatting conventions to apply consistently across all your sending.