Free Email Subject Line Grader | Chase Dimond
Free Email Marketing Tool

Email Subject Line Grader

Score your subject line and preheader text, preview your inbox, and get specific fixes. Built by Chase Dimond with $200M+ in attributed email revenue.

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How It Works

Eight criteria. One score. Specific fixes.

Most subject line tools are built for headlines, not emails. This grader scores the variables that actually determine whether ecommerce emails get opened, including preheader text, which no other free tool grades.

01
Length
Optimal range is 28–50 characters. Mobile clients truncate at ~40, cutting your hook before it lands. Too short and you're not giving readers a reason to open.
02
Spam Risk
Phrases like "click here" and "act now" trigger spam filters before readers ever see the email. We check against a curated list of filter-triggering words and constructions.
03
Curiosity Gap
If your subject line tells the full story, there's no reason to open. We detect genuine open loops vs. surface-level pattern matches that only look like curiosity.
04
Urgency and Scarcity
Without a reason to open now, most readers save it for later and never come back. We detect time-based and scarcity signals that reduce procrastination.
05
Personalization
Subject lines using "you" or "your" consistently outperform brand-centric lines. We check for direct reader address vs. broadcast language.
06
Power Words
A curated set of words that trigger emotional responses, not a bloated list padded with generic verbs. We flag when there aren't enough and when words are too spammy.
07
Emoji Usage
One emoji adds inbox distinction. Two or more signals low-quality content and can hurt deliverability. We evaluate whether emoji usage is helping or hurting.
08
Preheader Text
The second line of your inbox preview. We score whether your preheader extends the subject line's hook, adds new urgency, or wastes the most valuable real estate in email.
Why Trust This Tool

Built by someone who lives in the data

I'm Chase Dimond. I've been doing ecommerce email marketing since 2016 and have helped over 100 brands generate more than $200 million in attributed email revenue.

The criteria in this grader are distilled from thousands of A/B tests, hundreds of campaigns, and years of watching what actually moves open rates. The existing tools are built for blog headlines or generic marketing copy. This one is built for email marketers, by an email marketer.

The AI rewrite engine is context-aware. It knows whether you're writing an abandoned cart email or a welcome flow, and it rewrites accordingly. That distinction matters more than most tools acknowledge.

$200M+
Attributed Email Revenue
100+
Ecommerce Brands
100K+
Newsletter Subscribers
420K+
LinkedIn Followers
The Framework

How to write email subject lines that get opened

After a decade of email marketing and $200M in attributed revenue, here's what I know for certain about subject lines that perform.

1

Lead with the reader, not the brand

Most brands write subject lines about themselves. The reader doesn't care until they understand what's in it for them. Put the reader at the center of every subject line you write.

Before: "Summer Sale: Up To 40% Off"   After: "You deserve 40% off, just not for long"
2

Create an open loop, not a summary

A subject line that summarizes the email removes the reason to open it. Hint at something valuable without fully revealing it. Ask a question the email answers. Make a claim that requires the email to explain.

Before: "5 Tips to Improve Open Rates"   After: "The open rate trick we almost didn't share"
3

Use preheader text as a second hook

Most brands either leave preheader blank (wasted) or repeat the subject line (also wasted). The preheader is a second chance to earn the open. Use it to add urgency the subject line set up, reveal a detail that creates more curiosity, or include a specific benefit.

Subject: "The jacket is back"   Preheader: "Only 14 left, going fast"
4

Match the subject line to the email type

An abandoned cart email should feel different from a welcome email. Abandoned cart: urgency, specific product, recovery. Welcome: warmth, promise, what's coming. Win-back: honest, direct, no pressure. Using a promotional template for every email type is one of the most common and costly mistakes in ecommerce email.

5

A/B test one variable at a time

The only way to know what works for your specific audience is to test. Testing multiple variables at once tells you nothing actionable. Send A to 20%, B to 20%, auto-send the winner to the remaining 60%. Build a test log and you'll know your audience better than any tool can.

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Common Questions

Email subject line FAQ

The questions I get asked most often, answered directly.

A strong email subject line is 28–50 characters, creates a curiosity gap or urgency signal, speaks to the reader using "you" language, contains at least one power word, avoids spam trigger phrases, and uses emoji sparingly. The best subject lines give readers a reason to open now without revealing so much that opening becomes unnecessary.
Preheader text is the short preview text that appears after the subject line in the inbox, visible before the email is opened. Most email clients show 40–100 characters of preheader text. Used well, it extends the subject line's hook, adds urgency, or creates additional curiosity. Left blank or set to default, it wastes the second most valuable real estate in your email after the subject line itself.
The optimal length is between 28 and 50 characters. Most mobile email clients truncate subject lines at around 40 characters. Subject lines over 60 characters risk being cut off before the hook lands. Shorter subject lines under 20 characters can work for pattern interrupts but often lack context to drive opens.
Avoid "click here," "buy now," "act now," "limited time offer," "make money," "risk free," and "guarantee." Also avoid multiple ALL CAPS words, excessive exclamation marks, and more than two emoji. These trigger spam filters before readers ever see the message.
Yes, significantly. Abandoned cart subject lines should reference the specific product, create urgency around limited availability, and feel personal, like a reminder, not a broadcast. Promotional subject lines can be broader and benefit-focused. Using the same template for both is one of the most common missed opportunities in ecommerce email. Personalization and specificity are what make cart recovery emails convert at 2–5x the rate of standard campaigns.
A curiosity gap hints at valuable information without fully revealing it, compelling the reader to open the email to get the complete answer. "The open rate mistake most brands don't know they're making" creates a gap between what the reader knows and what they want to know. Subject lines that state the full benefit upfront give readers no reason to open. The key is that the email must actually deliver on the promise, curiosity gaps that disappoint train readers not to open.
According to Omnisend's 2025 Email Marketing Benchmarks, the average open rate for ecommerce emails is approximately 19.5%. Open rates above 25% are considered strong. Flow emails (welcome series, abandoned cart, post-purchase) typically outperform campaign emails because they reach subscribers at a relevant moment rather than on a broadcast schedule.
One emoji used strategically can increase open rates by adding visual distinction in a crowded inbox. Two or more emoji signal promotional or low-quality content and can hurt deliverability. Use a single emoji only when it genuinely adds meaning to the subject line, not as decoration.