What Makes Your Emails Look Like Spam and How to Avoid It

You sent a well-designed email — but instead of engaging with it, your recipients hit “Mark as spam.”

Why does that happen?

It’s not always because of your domain or email infrastructure. Often, it’s the email itself — how it looks, what it says, or who it’s sent to — that leads recipients to report it as unwanted.

And those manual spam complaints are much more damaging than you might think. Just a 0.3% spam complaint rate can prompt mailbox providers to throttle your sending reputation — and Mailmodo may even suspend your account to protect deliverability.

In this article, we’ll break down the real reasons people mark emails as spam and how you can avoid those costly mistakes using Mailmodo.

Why your email might come across as spam

Here are some common reasons recipients flag emails as spam, along with practical ways to avoid them:

1. Poor visual design makes your email feel suspicious

Emails that look cluttered, broken, or unprofessional often get flagged by users — not because of the content, but because of the way it’s presented.

Common design issues that make recipients uncomfortable:

• Image-heavy layouts with very little text

• Inconsistent fonts, colors, or overly promotional banners

• Layouts that don’t render properly on mobile devices

These design cues make your email feel generic or “mass-produced,” triggering users to question its authenticity.

Fix it with Mailmodo: Mailmodo’s no-code editor to design clean, responsive templates that look great on both desktop and mobile. You can preview how your email appears across devices before sending, ensuring a polished and trustworthy experience.

2. Subject lines that feel deceptive or overly promotional

One of the fastest ways to get marked as spam is to mislead your audience before they even open the email.

Subject lines that trigger suspicion include:

• ALL CAPS or multiple exclamation points (“LIMITED TIME OFFER!!!”)

• Misleading language that doesn’t match the actual content

• Overuse of urgency or manipulation (“Open NOW to avoid penalty”)

When recipients feel like they've been tricked into opening an email, they’re far more likely to report it.

Fix it with Mailmodo: A/B test your subject lines, experiment with tone, and use personalization to make your message feel relevant and respectful — not pushy. Mailmodo also lets you generate subject lines with AI, making it easier to strike the right balance between engaging and genuine.

3. Missing unsubscribe link or sender identity causes frustration

When users can't easily opt out of your emails, they’ll often hit the spam button as their only way out.

Here’s what frustrates them:

• No visible or accessible unsubscribe link

• No identifiable sender information in the footer

• Lack of clarity about who the email is from and why they’re receiving it

This creates a trust gap, and people assume you’re hiding something — which leads to spam complaints.

Fix it with Mailmodo: Mailmodo automatically includes unsubscribe links and sender footers in every email. You can customize the appearance, but the essential opt-out info is always there by default.

4. Broken personalization or dynamic content errors break trust

Nothing screams “this isn’t meant for me” like an email that says:

“Hi [FirstName], check out your personalized deal!”

Broken dynamic content not only looks careless, it creates a feeling of being “just another number” in a bulk send. This impersonality — combined with visible technical errors — often prompts recipients to hit “Report spam.”

Fix it with Mailmodo: Use Mailmodo’s preview and test tools to ensure dynamic content renders correctly for every contact. You can set intelligent fallbacks so even if data is missing, the message still feels clean and human.

5. Untrustworthy links or aggressive CTAs scare people off

When links don’t go where recipients expect — or when CTAs feel overly pushy — trust erodes quickly. Recipients start to wonder if your email is legitimate.

What causes that doubt:

• Links masked by shorteners or redirects to unrelated domains

• CTAs that scream urgency without context (“ACT NOW OR LOSE EVERYTHING”)

• Embedded forms in static emails that look suspicious

These red flags make users feel like they’re being manipulated or phished — so they mark the email as spam to protect themselves.

Fix it with Mailmodo: Mailmodo lets you build secure, AMP-powered interactive emails with embedded forms that follow best practices. You also get link tracking and visibility into what people actually click — so you can course-correct if something feels off.

6. Irrelevant content feels like a violation of trust

When users get emails that don’t match their interests — or worse, that they don’t even remember signing up for — they often assume you bought their data or added them without consent.

This is one of the top reasons people manually mark emails as spam, especially when:

• Content is unrelated to their past engagement

• Emails are too frequent or off-topic

• They don’t recall opting into your list

Fix it with Mailmodo: Use behavioral segmentation to ensure you're sending emails only to contacts who’ve shown interest in similar topics. Mailmodo also provides AI-powered segmentation, helping you create smarter engagement-based journeys that adapt to each user’s activity.

Conclusion

Spam complaints aren't always about malicious intent — sometimes, your email just feels irrelevant, suspicious, or annoying to the user. But the result is the same: damaged sender reputation and a lower chance of inbox visibility for future campaigns.

With Mailmodo, you can take the guesswork out of the equation. From visual design and personalization to segmentation and unsubscribe compliance, every piece is built to help your emails feel valuable and trustworthy.

Start improving your campaign quality by thinking like your recipients do. If you wouldn’t want to receive it, they probably don’t either and Mailmodo gives you the tools to fix that.