Header
In email marketing, the term header refers to two distinct things: the visual header section at the top of an email design, and the technical metadata headers that accompany every email message. The visual header is what recipients see: the top band of an email that typically contains the sender’s logo, a banner image, navigation links, or a prominent headline. The technical headers are invisible to recipients and contain routing and authentication information that mail servers use to deliver and verify the message.
The visual header sets the visual tone of the email, establishes brand identity, and is the first thing a recipient sees after opening. A well-designed visual header anchors the email’s identity and creates a consistent experience across every campaign. The technical headers, by contrast, include key fields like From, To, Subject, Date, and the outcomes of SPF, DKIM, and DMARC authentication checks. Email security tools and deliverability specialists read technical headers to diagnose delivery problems and trace the routing path a message took from sender to inbox.
For B2B email marketers, the visual header is an important design and brand asset: it should be sized correctly for both desktop and mobile, load quickly, include meaningful ALT text if it contains an image, and be consistent across the template library. The technical headers are managed by your email platform but are worth understanding when investigating deliverability issues, as they contain the evidence needed to diagnose authentication failures, routing problems, and spam filtering decisions.
What should a visual email header include?
A good visual email header should include your brand logo for immediate recognition, be appropriately sized for the email width (typically 600 pixels wide), and either set the visual tone of the campaign or provide navigation if it is a newsletter format. It should include descriptive ALT text for any image. Optionally, a header can include a web version link and a brief tagline. Keep it clean: the header should orient the reader, not compete with the body content for attention.
What are email technical headers?
Technical email headers are lines of metadata prepended to every email message that specify routing information, sender and recipient details, authentication results, and message identifiers. Key fields include From, To, Subject, Date, Message-ID, and X-headers added by email platforms and security tools. The Received headers show the routing path the email took through mail servers on its way to the recipient’s inbox.
Why do email headers matter for deliverability?
Technical email headers carry the authentication signatures and routing information that receiving servers use to evaluate whether an email is legitimate. The DKIM signature in the header is what receiving servers verify against your DNS records. When investigating deliverability problems, reading the technical headers of a bounced or spam-filtered email is often the fastest way to identify the root cause, as they contain the authentication pass or fail results and the complete delivery path.