What’s the difference between header and body content analysis?

Header analysis examines the technical envelope of your email: authentication records (SPF, DKIM, DMARC), routing information, sender/recipient addresses, subject line, and metadata. This analysis validates that you are who you claim to be, that your sending infrastructure is properly configured, and that you have permission to send from the stated domain. Header analysis happens early in the filtering pipeline-failing authentication can get you blocked before content is even examined.

Body content analysis evaluates the actual message: text content, HTML structure, images, links, and their combined patterns. This is where machine learning models assess whether your message looks like spam based on linguistic patterns, structural elements, link destinations, and similarity to known spam campaigns. Content analysis is more nuanced and context-dependent than header verification.

Both analyses contribute to filtering decisions, but they catch different problems. Authentication failures (header issues) suggest spoofing or misconfiguration-fundamental trust problems. Content flags suggest your message resembles spam regardless of sender legitimacy. You can pass header checks perfectly but still hit content filters, or vice versa. Complete deliverability requires passing both gates: be authenticated as a trusted sender AND send content that doesn't pattern-match to spam.