Header filters look at various elements, including:
1. Sender Information: This includes the senderâs email address, domain, and IP address. Ensure these are consistent and trustworthy. 2. Subject Line: Avoid misleading or spammy subject lines to prevent being flagged by filters. 3. Authentication Protocols: Implementing [DKIM](https://) (DomainKeys Identified Mail) and [SPF](https://) (Sender Policy Framework) helps in verifying the authenticity of your emails. 4. Content-Type: Ensure that your emails are properly formatted and include both plain text and HTML versions.