How to Keep Emails Out of Spam: Technical Setup and Content Rules

Email deliverability isn't magic or luck. It's a combination of technical settings and behavioral signals that mail providers read every time you hit Send. If even one element breaks down — the email goes to spam or doesn't get delivered at all.

This is a concrete breakdown: why it happens, what to configure at the domain level, what not to write in your emails, and how to check your sender reputation before a campaign goes nowhere.

Most business owners think spam filters only react to words like "free," "limited offer," or subject lines in ALL CAPS. In reality, mail providers analyze dozens of signals simultaneously — and technical ones carry far more weight than the text itself.

No domain authentication. If your domain isn't configured with SPF, DKIM, and DMARC, the recipient's mail server can't verify the email actually came from you and not someone spoofing your address. By default, that email is suspicious.

Damaged IP or domain reputation. If you've previously sent to dead contact lists, had high spam complaint rates, or suddenly scaled up your sending volume — providers remember. Reputation builds over months and collapses in a few bad campaigns.

Content that triggers filters. Spam words, broken HTML, missing unsubscribe links, images with no text — all of this automatically lowers your email's "score" before a human ever sees it.

At Brutal Marketing, we regularly run into this situation: a company has been sending campaigns from their corporate domain for years with zero authentication — and everything seemed fine. Then Gmail updates its algorithms and deliverability drops from 90% to 40% in a month. Same root cause every time — no DKIM.

The tricky part is that spam placement isn't always visible in your ESP's stats. An email can technically "deliver" but land in the Spam folder — and the platform counts it as a successful delivery.

This is the foundation. Without it, nothing else matters. Let's break down each tool — what it does and how to set it up.

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to every email, confirming that the message hasn't been altered in transit and genuinely came from your domain.

Your ESP (Mailchimp, SendPulse, ActiveCampaign, etc.) generates a key pair. The private key lives on the sending server; the public key is published in your domain's DNS. When the email arrives, the recipient's server verifies the signature against DNS.

A DKIM setup typically means adding a TXT record like this:

selector._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GCS..."

selector is a name assigned by your ESP — commonly mail, k1, smtp, etc.

Practical tip: after setting up DKIM, verify it through MXToolbox or mail-tester.com. A passing signature already puts you ahead of roughly 70% of senders in your segment.

DMARC (Domain-based Message Authentication, Reporting and Conformance) tells the receiving server what to do when SPF or DKIM fails — and sends you reports on who's using your domain and how.

A basic DMARC record:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

p=none means collect reports only, block nothing. This is your starting point. Once you've confirmed everything is set up correctly, move to p=quarantine (email goes to spam) or p=reject (email is refused entirely).

Since 2024, Google and Yahoo require DMARC for anyone sending more than 5,000 emails per day. For lower volumes it's a recommendation, not a hard requirement. At Brutal Marketing, we advise setting up DMARC even if you're sending 500 emails a month — it protects domain reputation and gives you data to work with.

BIMI (Brand Indicators for Message Identification) is a newer standard that lets you display your brand logo next to emails in supporting mail clients. It doesn't dramatically impact deliverability on its own, but it improves brand recognition and open rates. Requires a valid DMARC record with p=quarantine or p=reject.

Even with perfect technical setup, bad content can ruin everything. Spam filters analyze your text, HTML structure, links, and even the ratio of images to text.

Classic triggers: "free," "100% guaranteed," "urgent," "today only," "earn money fast," "click now." But modern filters are smarter than that. They look at context and concentration, not individual words.

If one email combines an aggressive CTA, a massive discount, and zero personal address — that's already a red flag. Write like a person talking to a person, not like a highway billboard.

Broken markup is one of the fastest routes to spam. If your email contains malformed HTML, unclosed tags, or unnecessary attributes — filters treat it as a sign of auto-generated spam.

A few rules:

• avoid heavy use of <font>, <b>, <i> tags without CSS;
• don't hide text (matching font and background color);
• don't use display:none to conceal content;
• keep email file size under 100 KB — larger emails raise more suspicion.

An email that's just one large image is a classic spam pattern. Filters can't "read" images, so if there's no text content — the email looks suspicious.

The safe ratio: at least 60% text to 40% images. Always include alt text on images.

A missing unsubscribe link is a direct violation of regulations in most markets (GDPR, CAN-SPAM) and a hard signal for filters. If someone can't opt out, they'll hit "Report Spam" — and mass complaints destroy domain reputation.

The unsubscribe link must be visible, one-click, and actually functional. Don't bury it in tiny print under the copyright notice.

Emails with zero personalization — "Dear Customer" instead of a name — get opened less and get manually marked as spam more often. Even basic first-name personalization increases trust.

If your CRM is integrated with your ESP, personalization takes a few minutes to set up. We covered how to build that kind of integration in our piece on automating email campaigns through CRM — with specific examples for popular platforms.

Technical settings are in place, content is clean — but emails still land in spam? Time to check your domain and IP reputation.

Google Postmaster Tools — a free service from Google that shows your domain and IP reputation among Gmail users, spam complaint rates, authentication status, and delivery errors. Essential for anyone sending to Gmail addresses.

To get started — verify your domain via a DNS record and wait for data to accumulate (you'll need at least a few hundred emails sent to Gmail).

MXToolbox (mxtoolbox.com) — checks DNS records (SPF, DKIM, DMARC), blacklists, and MX records. One of the most widely used free tools for technical audits.

Mail-Tester (mail-tester.com) — send a test email to a generated address and get a score from 0 to 10 with a detailed breakdown: authentication, content, links, HTML structure.

Sender Score (senderscore.org) — a reputation score for your IP from 0 to 100. Below 70 means problems. Below 50 means most providers are already blocking or filtering you.

Blacklist check — verify your IP and domain against major blacklists: Spamhaus, Barracuda, SORBS. Getting listed can happen from mass complaints or technical errors. Getting removed is harder: you'll need to fill out a request form and wait.

First, stop bulk sending. Continuing to send with a bad reputation is like pouring fuel on a fire.
Second, clean your list. Remove inactive subscribers, unsubscribes, and hard bounces (addresses that don't exist). A clean list is the foundation of good reputation.

Third, start warming up the domain. This means gradually increasing sending volume: week one — 50 emails per day, week two — 200, week three — 500, and so on. Only to your most engaged audience — people who open and click.

For more on building a systematic approach to contact database management and CRM segmentation, check out our piece on setting up a sales funnel in CRM — the principles translate well, even in a different context.

At Brutal Marketing, we run through this list before every bulk send. Save it and adapt it to your setup.

•  Test email sent to mail-tester.com — score is 8/10 or higher
•  Test email reviewed in Gmail, Outlook, and a mobile client
•  Google Postmaster Tools shows domain reputation as "High" or "Medium"

If even one item on this list is unchecked — don't send the campaign. One bad send can cost you months of reputation recovery.

The Brutal Marketing team offers a wide range of features that cater to the same needs and make the sales process truly smooth and seamless. If you want to learn more about the positive impact this intuitive sales CRM can have on your business, feel free to contact us.

Pipedrive, Kommo — these are just a few examples of intelligent CRMs for businesses that can help you optimize your sales process to achieve your sales goals. Advanced CRMs are used by sales teams of various sizes.

With this high-quality sales tool, you can create multiple sales pipelines for efficient management of the sales process stages. You can add, edit, and rename your sales deals. By using the CRM, it's easy to track the customer journey.

We at Brutal Marketing will select the best CRM program for you to use in your business. We will be happy to tell you about the program's capabilities and show you which settings will exactly help you achieve the desired financial results.

If your emails regularly land in spam — or you're just getting started with email marketing — we're ready to help you get it right. At Brutal Marketing, we set up domain authentication, connect your ESP to CRM, build out contact segmentation, and write email sequences that actually reach readers.

One client result after a technical audit and domain warm-up: deliverability went from 54% to 91% in six weeks, open rate climbed from 8% to 23%.

Leave a request on our CRM implementation services page — we'll review your situation and put together a concrete action plan.