# Newsletter glossary — Letterhead

Source: https://www.tryletterhead.com/glossary.html

_Newsletter glossary_

# The terms, defined like a practitioner would.

What audience teams, editorial teams, and revenue teams actually mean when they use the words. Built from inside the workflow, not pulled from a textbook.

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_Glossary_

## Newsletter terms, defined.

### Open rate

Percentage of delivered emails opened. Useful as a directional signal; less useful since Apple Mail Privacy Protection started auto-loading images. Pair with click rate and reading time.

### Click-through rate (CTR)

Clicks divided by delivered. The honest engagement metric, post-MPP. Worth segmenting by content type — recommendations click differently than headlines.

### Sender reputation

How mailbox providers grade your domain and IP. Built from engagement, complaint rate, bounce rate, and authentication. Drifts slowly until something breaks; then drops fast.

### List hygiene

Removing addresses that hurt your reputation. Hard bounces, long-term unengaged, role accounts, traps. A weekly workflow, not a quarterly project.

### Direct-sold sponsorship

Inventory you sell yourself to a specific brand for a fixed run. Higher CPM than programmatic; takes more sales work. The bread and butter for most editorial newsletters.

### Programmatic ad fill

Inventory filled automatically through ad networks (GAM, LiveIntent, RevContent). Lower CPM, higher fill, no sales overhead. Best as the backstop on slots that don't sell direct.

### House promotion

Cross-promotion of your own products — other newsletters, paid tiers, events, products. The most efficient inventory you have if you actually use it.

### Engagement segment

A subscriber group built from interaction patterns, not declared attributes. The audience that opens every send is a different audience than the one that opened twice last quarter.

### Pre-flight

Automated checks that run before send: brand guidelines, broken links, spam-score, clipping risk, render quality across providers. Catches the things QA misses at midnight.

### Clipping

When Gmail truncates an email over ~102KB and adds a "View full message" link. The bottom of your newsletter — including unsubscribe and ad slots — disappears. Avoidable with slim HTML.

### Authentication (SPF / DKIM / DMARC)

The three records that tell mailbox providers your sends are legit. Breaking one silently is the most common cause of an overnight engagement drop.

### Newsletter portfolio

A set of related newsletters run by one team or company. The unit of analysis for audience teams who care about cross-newsletter behavior, overlap, and growth.

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