Understanding Spam Filters in 2025: Why Retail Marketing Emails Get Blocked & What You Can Do

Key Takeaways:

Gain a better understanding of spam filters.

Find out which spam phrases to avoid and get inspired by creative alternatives.

Learn some best practices when crafting email subject lines and preview texts.

Imagine this: You’re running a big sale and craft the perfect email: “LIMITED TIME ONLY! HUGE DISCOUNTS—BUY NOW!” You hit send, expecting a flood of orders. But instead? Crickets.

It turns out your email never made it to most inboxes. It got flagged as spam, buried in the junk folder where no one will ever see it. Sound familiar? If your emails aren’t getting delivered, spam filters could be the culprit.

Retailers have it especially tough when it comes to email deliverability. Because so many promotional emails flood inboxes every day, ISPs (internet service providers) and email platforms like Gmail and Outlook have gotten stricter about what they let through. But that doesn’t mean you’re out of luck — it just means you need to be smart about how you write, format, and send your emails.

Here’s what you need to know about spam filters and how to keep your retail emails front and center in your customers’ inboxes. We’ll also share a curated list of email spam words you should avoid to help boost your open rates.

Why Spam Filters Target Retail Emails

As a retailer, you’re constantly running sales, promotions, and product launches. The problem? Spam filters are programmed to be extra suspicious of emails with certain sales-heavy words like “free,” “discount,” “limited time,” and “urgent.” These are common red flags because scammers and spammers have abused them for years. Here’s a list of spam words that marketing experts recommend avoiding:

Promotional Language:

Urgency and Scarcity:

Manipulative or Deceptive Language:

Financial Incentives:

And it’s not just the words you use, but also how often you send emails. If you’re blasting out daily promotions with little personalization, ISPs might see your emails as low-value and start filtering them out. Even worse, if recipients mark your emails as spam (even accidentally), that can hurt your sender reputation, making it even harder for future emails to land in inboxes.

The key takeaway? You need to find a balance between writing compelling promotional emails and making sure they don’t look like spam.

Striking the Right Balance Between Promotional & Trustworthy Language

Instead of using aggressive, pushy phrases like “buy now” or “act fast,” try wording your emails in a way that feels more engaging and personal. For example, instead of “Don’t Miss Out! Huge Sale – Buy Now!” you could try “A Personalized Pick for You” or “You’ll Love What’s Inside.” And instead of “Limited Time Only – Final Hours!” try “Still Thinking About It? Here’s Something Just for You.”

This simple shift makes your emails sound less spammy and more like a conversation. Plus, well-crafted subject lines and preview text (the little snippet of text that appears in the inbox) can help increase open rates. Instead of shouting, make your emails feel like they’re offering something personalized (without saying “special offer” or “exclusive deal”).

Here are some spam-word-free email subject lines to inspire you (and lift your open rates):

• “We picked this just for you – take a look!”
• “Your next favorite _________ is waiting…”
• “Only a few left! Get yours before they’re gone.”
• “Love a good deal? You’ll want to see this.”
• “A little surprise inside – open up!”
• “Your wish list just got better.”
• “We saved this for you – but not for long!”
• “Trending now: The must-have styles of the season.”
• “You asked, we listened! Meet our newest arrivals.”
• “This won’t wait—see what’s new before anyone else!”

Formatting & Design Mistakes That Trigger Spam Filters

It’s not just the words you use. How your email looks also plays a big role in whether or not it gets flagged as spam. Here are a few things that can get your email sent to the spam folder:

All Caps

A subject line like HUGE SALE—SHOP NOW might grab attention, but it also screams “spam!” to email filters. Keep it simple.

Too Many Exclamation Points

Using one is fine. Using three or more? That’s a red flag.

Heavy on Images, Light on Text

Emails that are mostly images with little to no text can be a problem. Spam filters prefer a good balance between text and visuals.

Forgetting Alt Text for Images

If your images don’t load, will your message still make sense? Always add alt text to ensure your emails are readable even if images don’t display.

Prioritizing Personalization & Engagement When Crafting Emails

One of the best ways to avoid spam filters (and keep your customers engaged) is to make your emails feel personal. According to recent data from Litmus, 80% of email marketing pros report that personalization tactics like subject line personalization, adding real-time content, and using dynamic message personalization improve performance.

So, instead of sending the same generic message to everyone, try personalizing emails based on customer behavior. Here are a few tips for email subject line and preview text best practices:

Use first names

Emails that greet customers by name tend to feel more genuine.

Recommend products based on past purchases

If someone bought winter boots last month, a follow-up email with matching accessories makes sense.

Segment your audience

Not every subscriber needs to see every sale. If someone shops for women’s clothing, sending them promotions for men’s sneakers isn’t helpful. Per recent research from Litmus, 90% of email marketing experts found that using subscriber segmentation to fine-tune their messages increased their emails’ performance.

Keeping Your Retail Emails Out of Spam

No one wants their emails to be ignored — or worse, sent straight to the spam folder. The good news? By being mindful of the words you use, keeping your email design clean, and making your content feel personal, you can dramatically improve deliverability.

Get More from Your Retail Emails with Klaviyo

Struggling with deliverability and engagement? Our Klaviyo Email Marketing Program will help you send smarter, high-converting emails to your retail customers.

Learn More