How to Stop Your Emails from Being Marked as Spam

No matter what type of business or industry you’re in, email marketing should be a priority. It’s still one of the most reliable ways to reach your audience, nurture relationships, and drive conversions—without being at the mercy of algorithm changes.

Marketers consistently cite email as a top channel for lead generation and ROI, which is why deliverability and trust are just as important as copy and design.

If you’re working to strengthen your email strategy, you’re on the right track.

But blasting more promotional emails doesn’t automatically mean better results.

Some of your messages may get filtered—or worse, recipients might mark them as spam.

Even when you carefully craft your content, you might not see the performance you expect. Why?

Because there are several technical, legal, and user-experience pitfalls that can trigger spam filters or complaints. This guide shows you how to avoid them.

Even if you aren’t facing deliverability issues today, understanding these principles prevents future problems and keeps your emails effective.

Ideally, your emails should land in the inbox, get opened, and lead to meaningful actions. None of that happens if your messages are flagged as spam.

Without careful planning—especially around consent, frequency, and authentication—you risk being treated like a spammer.

And simple copy or formatting mistakes can escalate into serious brand and legal issues.

Keep this guide handy as your deliverability checklist. Let’s dive in.

How Consumers Define Spam

Spam used to be easy to spot.

You’d get unsolicited messages with odd symbols in the subject line or claims that you’d won a contest you never entered—from senders you didn’t recognize.

Many of those messages also contained shady or inappropriate content that nobody asked for.

And in earlier days, some included malicious links or attachments.

Modern email providers catch the obvious stuff. Those messages usually land straight in the spam folder.

But here’s the shift: today, even legitimate brands can get flagged as spam because consumer expectations have evolved.

People mark messages as spam even when they recognize the sender—and even when they opted in—if the content feels irrelevant, too frequent, or hard to unsubscribe from.

That’s a big change for email marketers.

So yes—someone who willingly joined your list can still send your messages to spam.

Studies show a leading reason for spam complaints is getting too many emails or irrelevant content.

What does this mean for you?

Even reputable brands emailing willing subscribers are at risk if they mismanage expectations, frequency, or relevance.

Before we get tactical, let’s cover the legal basics every sender should know.

Understanding the Law

Quick disclaimer: we’re not lawyers. The following is based on research. Consult a qualified attorney to ensure full compliance with all applicable laws and regulations.

In the early days of email, bad actors abused the channel, which led to legal frameworks to protect consumers.

The CAN-SPAM Act of 2003 set national standards for commercial email in the U.S. and is enforced by the Federal Trade Commission (FTC).

Its full name—“Controlling the Assault of Non-Solicited Pornography and Marketing Act”—reflects its goal: reduce unwanted, deceptive messages.

Don’t panic—compliance is straightforward if you follow the FTC’s guidance and respect subscriber choice.

Here’s a summary of the key guidelines from the FTC’s official compliance guide:

Key CAN-SPAM Guidelines

1. Don’t use misleading header information: “From,” “To,” “Reply-To,” and routing info must accurately identify the sender.
2. Don’t use deceptive subject lines: The subject must reflect the message’s actual content.
3. Clearly identify ads: If your message is an advertisement, make that disclosure clear and conspicuous.
4. Include a physical address: Add a valid postal address (street address, P.O. box, or commercial mail receiving agency).
5. Provide an easy opt-out: Give recipients a clear, simple way to unsubscribe (no logins or hurdles).
6. Honor opt-outs promptly: Process requests within 10 business days, and keep the opt-out mechanism working for at least 30 days after you send.
7. Monitor vendors: If a third party sends on your behalf, you’re still responsible for compliance.

Violations can lead to significant per-email penalties (adjusted annually for inflation). In short: treat consent and transparency as non-negotiables.

Before sending any campaign, confirm with legal counsel that your program aligns with applicable laws (and consider other regimes like GDPR, UK PECR, and Canada’s CASL if you email internationally).

Bottom line: earn permission and respect it.

Now, let’s move on to our top 11 tips to prevent your emails from being flagged as spam.

1. Avoid Buying Email Lists

Even people who opted in may complain if your content feels off. Sending to people who never consented is far riskier.

Buying lists often violates email service provider terms and can violate privacy laws outside the U.S. (and in some U.S. states, depending on how data was collected). It also tanks engagement and can trigger spam traps.

U.S. CAN-SPAM doesn’t require opt-in, but it does require honesty and easy opt-outs. Best practice—and the only approach that consistently works—is permission-based marketing.

Most inboxes are already overflowing. Unsolicited emails from unfamiliar brands won’t get attention; they’ll get complaints.

Focus on growing your own list with clear value exchanges (lead magnets, VIP access, exclusive discounts) and transparent consent language.

Result: higher engagement, stronger reputation, and far fewer spam flags.

2. Limit How Often You Send Emails

You think about your brand all day—your subscribers don’t. Respect their inboxes.

Sending too frequently causes fatigue, unsubscribes, and complaints. Start with a predictable cadence (weekly is a safe baseline for many brands), then adjust based on engagement and subscriber preferences.

Better yet, offer a preference center at signup and in your footer so people can pick cadence (e.g., “weekly roundup,” “only sales,” or “pause for 30 days”). This reduces “mark as spam” clicks.

Also note that major inbox providers now expect bulk senders to support one-click unsubscribe. Make it simple.

Give subscribers control, and your complaint rate—and spam folder risk—drops.

3. Use a Clear and Recognizable “From” Address

Make it instantly obvious who the email is from.

Use a consistent, branded address (e.g., newsletter@yourdomain.com) and a friendly, recognizable sender name. Avoid generic or confusing addresses like donotreply@ or random strings.

Send from your own domain (not a free mailbox provider) and keep “From” details stable across campaigns to build recognition and trust.

If you must use multiple mailboxes (e.g., support@, sales@), keep promotional mailings to a single, trusted identity.

4. Don’t Trick Your Recipients

Avoid clickbait. Short-term opens aren’t worth long-term damage to sender reputation.

Misleading “Fwd:” or “Re:” subject lines, fake deadlines, bait-and-switch offers, or promising giveaways that don’t exist will drive complaints.

Keep the subject line and preview text aligned with the content inside. Deliver exactly what you promise.

And don’t try to hide text in images or use tricks to bypass filters—machine learning systems and humans will catch it.

5. Choose a Reliable Email Service Provider

Select a reputable ESP with strong deliverability tooling—think authentication support, list-unsubscribe headers, bounce handling, suppression lists, and feedback loop integrations.

Quality providers actively enforce anti-abuse policies, help you maintain list hygiene, and provide deliverability analytics (like inbox placement tests and spam complaint monitoring).

Cut-rate platforms with lax policies can get entire IP ranges or domains blocklisted—taking your program down with them.

6. Authenticate Your Domain and Warm Your IP

Modern deliverability starts with authentication and reputation, not “IP certification.” Set up:

• SPF (Sender Policy Framework) for your sending domain.
• DKIM (DomainKeys Identified Mail) with aligned signing.
• DMARC with a policy (start at p=none to monitor, then move to quarantine or reject once you’re confident).
• BIMI (optional) to display a brand logo in supported inboxes after DMARC enforcement.

If you use a dedicated IP, warm it up—start with low volumes to your most engaged subscribers and ramp gradually. For shared IPs, keep your list clean so you’re a positive contributor.

Monitor domain reputation via tools like Gmail Postmaster. Aim for a very low complaint rate (keep it well under common thresholds).

7. Set Clear Expectations

When someone opts in, immediately confirm what they’ll receive and how often. Setting expectations reduces surprises—and complaints.

Clarify these expectations:

• Content: Be explicit about what they’ll get—newsletters, product updates, promotions, or all of the above. Example:
• Frequency: Tell people how often you’ll email and stick to it. Offer a preference center to adjust cadence instead of forcing a single schedule.
• Design & sender: Keep the layout consistent and professional, and use the same recognizable “From” name and address.

8. Stay Relevant

Before hitting send, ask: “Why this message, for this subscriber, right now?” If the value isn’t clear, rethink it.

Subscribers don’t need reminders that you exist—they need timely, useful content tied to their interests or lifecycle stage.

For example, a furniture retailer sending generic weather updates feels irrelevant. A limited-time discount on a category they browsed—or a setup guide for an item they purchased—adds value.

Lean into triggered and lifecycle emails (welcome, post-purchase, re-engagement) and use personalization beyond just a first name.

9. Segment Your List

Segment by behavior (browse, purchase, engagement), demographics, interests, and lifecycle stage. The tighter the segment, the higher the relevance—and the lower the complaint rate.

Practical ideas: send different content to new vs. long-time subscribers, tailor offers by category affinity, suppress recent purchasers from generic promos, and “sunset” chronically inactive contacts.

Better targeting boosts opens and clicks and protects your sender reputation.

10. Master Your Subject Lines

The subject line is your first impression. Keep it concise, specific, and aligned with the email’s value. Front-load the most important words so they don’t get truncated on mobile.

Pair it with compelling preview text that complements—not repeats—the subject. Avoid ALL CAPS, excessive punctuation, and spammy phrasing.

Personalization can help (topic, product category, or benefit they care about), but test everything. There’s no universal “best length” or formula—your audience decides.

Use A/B tests to learn what resonates. Curiosity, clarity, and honest urgency typically outperform vague hype.

11. Check Spam Risk Before Sending

Most ESPs offer pre-send checks. Use them to validate authentication, scan content, and preview across devices and dark mode.

Avoid patterns that correlate with filtering: image-only emails, excessive special characters or colors, tiny “wall of links” footers, URL shorteners, and oversized messages. Always include a readable plain-text version.

Mind your language. Context matters more than any one “trigger word,” but over-promotional phrasing (especially in finance/ecommerce) can hurt. Keep it natural and specific to the offer.

Finance words that often underperform out of context:

• $$$
• Affordable
• Bargain
• Beneficiary
• Best price
• Cash

Ecommerce phrasing to use carefully and honestly:

• Buy
• Order now
• Clearance
• Shopper

Technical checks matter, too: test links (HTTPS), ensure images have alt text, verify your sending domain isn’t on blocklists, and keep your complaint rate low by removing chronically inactive or unengaged contacts.

If your pre-send score or inbox test looks risky, revise the content, narrow the segment, or reduce volume and retry.

Conclusion

Email is a powerful, high-ROI channel—but only if your messages reach the inbox and feel welcome when they do.

The bar has risen. Even trusted brands get flagged when they send too often, ignore preferences, or skip authentication.

Focus on consent, clarity, and relevance. Set expectations, authenticate your domain, keep lists clean, and let subscribers control frequency.

Use your ESP’s deliverability tools, test before sending, and watch your complaint rate and engagement closely.

Do these consistently, and you’ll improve deliverability, protect your sender reputation, and turn more emails into opens, clicks, and revenue.