Ever poured your energy into crafting the perfect marketing email, only to have it land straight in someone’s spam folder? With inboxes getting smarter (and stricter), even well-intentioned emails can get flagged. For brands relying on email marketing to reach customers, deliverability is everything.
If your email doesn’t make it to the inbox, it might as well not exist. That’s why learning how to avoid spam filters when sending emails is important. In this post, we’ll break down what spam filters actually do, explore the right words to avoid spam filters, and share smart strategies to boost your email deliverability.
What Is a Spam Filter on Email?
In simple terms, a spam filter is like a gatekeeper. Email service providers (like Gmail, Outlook, and Yahoo) use spam filters to weed out unwanted, unsafe, or overly promotional messages before they ever reach a user’s inbox.
Spam filters look at a variety of signals, including:
- Email content: Does it contain risky phrases or formatting?
- Sender reputation: Has the sender previously sent spammy emails?
- Engagement history: Are recipients opening, clicking, or replying—or ignoring and unsubscribing?
- Technical setup: Is the sender’s domain authenticated properly?
For marketers, this means that vigilance is essential. Even if your email has value, if it looks or feels like spam to a filter, it could get sidelined. It’s not just about avoiding certain words, although we’ll get to those soon. It’s about your entire email strategy: content, formatting, audience, and infrastructure.
Common Spam Trigger Words and Phrases
Spam filters are trained to spot language that’s overused, misleading, or commonly associated with scams, and if you’re not careful, even a legitimate offer could be mistaken for junk.
There’s no official blacklist, but marketers know to tread lightly around certain high-risk phrases. Here are some common words to avoid spam filters, especially in subject lines and calls to action:
- Free – Sounds like clickbait if not contextualised properly.
- Guaranteed – Filters don’t trust promises that seem absolute.
- Winner – Often tied to fake prize or lottery scams.
- Urgent / Act now / Limited time offer – Pushy or false urgency can be a red flag.
- Click here – Overused and often linked to phishing attempts.
- Make money / Earn money / Be your own boss – Classic “get-rich-quick” language.
- Risk-free / No cost / 100% free – If it sounds too good to be true, filters may agree.
- Congratulations / Free gift / No strings attached – Common in low-trust promotional emails.
- Credit / Subject to approval / Unsecured – These phrases can mimic spam from loan or credit scams.
- This isn’t a scam – If you have to say it, filters are already suspicious.
But don’t worry, you don’t need to cut all promotional language. Instead, rewrite these phrases naturally. For example:
- Instead of “Act now!”, try “Spots are filling up fast.”
- Instead of “Free gift”, say “You’ll receive a surprise bonus with your order.”
- Instead of “Click here”, use “View details” or “Explore the offer”.
It’s all about tone, trust, and context. Keep your messaging human and helpful, not salesy or spammy.
Content and Formatting Best Practices
Even if your wording is on point, your design and structure can trip you up. Spam filters evaluate your entire email format, not just the text. Here’s how to keep your message clean and avoid spam filters when sending emails:
- Be honest in your subject line
Avoid clickbait. Your subject should clearly reflect what the reader will find inside the email. - Don’t overdo punctuation or CAPITAL LETTERS
Multiple exclamation marks!!! and SHOUTY CAPS can feel aggressive and spammy. Stay cool. - Watch your formatting
Stick to simple fonts, avoid rainbow-coloured text, and limit bold/highlighted copy. - Balance images and text
Emails that are image-heavy (or just one big graphic) can trigger spam filters. Make sure you have enough plain text to explain your message clearly. - Mobile matters
Most South Africans read emails on their phones. Make sure your layout adjusts seamlessly across devices.
When in doubt, preview and test! You want your emails to feel professional, accessible, and easy to read, on any screen, in any inbox.
Technical Tips to Improve Deliverability
Beyond the words and layout, your email’s technical setup plays a major role in getting it past spam filters and into your recipient’s inbox. Here are a few steps to help keep your emails clean and credible:
- Authenticate your domain
Setting up SPF, DKIM, and DMARC records tells email providers that you’re a legitimate sender. It’s essential for avoiding spoofing and improving trust. - Use a reputable Email Service Provider (ESP)
Sending from a trusted platform helps ensure consistent deliverability. Good ESPs also offer built-in tools to help you avoid spam triggers. - Clean your email list regularly
Remove invalid, inactive, or disengaged addresses. High bounce rates and low open rates can damage your sender reputation over time. - Encourage real engagement
The more recipients open, click, or reply to your emails, the more inbox providers will trust your future sends. Ask questions, offer value, and make it easy for readers to respond.
Final Checks Before Sending
You’ve got great content, clear formatting, and your tech is in order, now for the final polish:
- Use spam-check tools
Email deliverability tools or your ESP’s built-in spam checker can flag risky elements before you send. - Test across email clients
Preview how your message looks on Gmail, Outlook, Apple Mail, etc. Formatting can change between inboxes. - Include clear sender details
Use a recognisable “from” name and always include a proper email signature with your business name and contact info. - Always include an unsubscribe link
Not only is this legally required, but it also builds trust. Make opting out easy and respectful.
These small steps go a long way in protecting your deliverability and keeping your email reputation intact.
Need help refining your email strategy? Explore Ruby Digital’s email marketing services and let us help you send smarter, not harder.
Because great emails deserve to be seen!
