According to Kaspersky, 44.99% of global email traffic was spam in 2025. Nearly half of all emails never reach a human. They get filtered or buried before anyone reads them.

If your cold outreach gets no replies, the problem might not be your copy. It might be that your emails never land in the inbox at all.

In this post, I’ll walk you through the 9 steps I use to keep my cold emails out of spam and into primary inboxes, covering authentication, warmup, monitoring, and everything in between.

When you hit send, your email passes through AI-powered spam filters guarding your recipient’s inbox.

Email deliverability, usually expressed as a percentage, measures whether your email reaches the primary inbox.

Spam filters use several techniques to decide what gets through:

The goal is clear: your email should land in the primary inbox, not the junk or spam folder.

Different email clients have different criteria for success. Gmail categorizes emails into tabs (promotions, social, updates) in addition to the primary inbox. Ensuring your email lands in the primary tab is the difference between getting read and getting ignored.

Following this email deliverability checklist helps make sure your emails reach the primary inbox.

Internet Service Providers (ISPs) filter spam aggressively, and that spam now makes up nearly half of all email traffic. Test your deliverability before starting any cold email campaign.

These tests keep your legitimate emails from being mistakenly labeled as spam. Keeping your spam rate low protects your sender reputation.

Most email deliverability tests return a score you can track over time. Aim for a high deliverability rate with a low bounce rate.

Run regular cold email audits too, so you catch reputation drops before they cost you replies.

Send a quick message to your recipients asking for confirmation of receipt. This method is simple and direct.

Give a brief contextual overview of your initial email and be polite.

Sending cold emails? Try these tested follow-up templates to secure more replies.

Keep an eye on bounce notifications. They indicate your emails haven’t been delivered.

In Gmail, click on the “Show original” option in sent emails by clicking the three-dot menu.

A new tab opens with the full header. Click “Copy to clipboard,” then go to Google’s messageheader tool, paste the header text, and click “Analyze” for feedback on delivery status.

Outlook users can rely on delivery receipts or the Tracking feature. Apple Mail users should activate Delivery and Read Receipts.

For detailed guidance, check out How to see if someone read your email.

Extensions like MailTrack and Email Tracker by Mailtag let you see when and how often your emails are opened.

Email automation tools let you track open rates, clicks, and replies in a single dashboard.

Explore lemlist if this option interests you. Here’s a snapshot of our campaign analytics dashboard:

The deliverability landscape includes authentication checkers, warmup tools, seed-list inbox-placement testers, blacklist monitors, and sender-reputation dashboards. Most outbound teams cobble together multiple tools to cover all the bases.

Here’s how we approach it at lemlist:

Deliverability Setup handles automated domain provisioning and configures SPF, DKIM, and DMARC for you. Every seat includes lemwarm, which runs automated warmup conversations to build your sender reputation before you launch campaigns.

Deliverability Hub runs Deliverability Boost checks before you send, catching issues that could hurt placement. Inbox rotation spreads sending across multiple mailboxes to protect each domain’s reputation at scale.

Monitoring & alerts runs inbox-placement tests across Google and Microsoft. It flags blacklist hits or domain health issues and sends alerts so you catch problems before they tank your campaigns.

We have a comprehensive email deliverability checklist if you want a step-by-step breakdown. Here’s an overview of the basics:

Sending emails in bulk? Just like warming up before physical activity, your emails need to ease into the sending process.

Begin by sending a few emails per day and gradually increase the number. This warm-up period (typically several weeks) acclimatizes your domain to the digital environment and boosts your deliverability score. Learn how to warm up your email account.

Investing in a professional ESP can significantly enhance your email deliverability. Think of an ESP as a skilled postman, ensuring your emails are delivered correctly and efficiently.

Personalized emails build a connection with the recipient and increase engagement. Our own cold email analysis puts the average reply rate at 5 to 8%, and strong personalization is one of the biggest levers for beating that.

Here’s a resource to master email personalization at scale.

Regularly update your email list so you’re not sending emails to outdated addresses. A large share of the workforce changes jobs each year, so keeping your list fresh can drastically reduce bounce rates.

Verify all emails before using them. You can clean your list by removing hard bounces, and lemlist’s email finder and verifier can help you validate contacts upfront.

A significant share of emails are opened on mobile devices, so mobile optimization is critical. Emails not optimized for mobile are often deleted or marked as spam.

Quick don’ts to keep in mind:

Using a custom domain? Understand and implement authentication protocols like DNS, SPF, DKIM, and DMARC. These act as security checkpoints for your emails, ensuring safe passage to the inbox.

Google’s sender guidelines require anyone sending about 5,000 or more messages a day to Gmail to authenticate with SPF, DKIM, and DMARC and keep their reported spam rate below 0.3%.

You can either set these records up yourself or set up SPF, DKIM, and DMARC automatically with lemlist’s Deliverability Setup.

Stay compliant with regulations like GDPR to avoid hefty fines. Use a reliable email verifier to reduce bad data and support compliance.

Focus on sending quality emails rather than mass emailing. Targeting the right people is key to higher engagement rates (and better email deliverability).

If you’re pushing bulk campaigns, ensure your contact lists are correctly segmented.

Yes, images won’t automatically doom your emails to the spam folder. Balance is key. We wrote an entire post about whether images send your cold emails to spam if you’re interested.

Not essential, but a custom tracking domain can safeguard your main domain’s reputation. We created a guide on custom tracking domains.

Emojis are like spices. A little can bring life, but too much might spoil the dish. Test their impact and use them sparingly to avoid spam filters. Here’s a data-backed guide on how to use emojis in cold emails.

Length isn’t a deal-breaker, but crisp, focused emails usually win the race. Keep it valuable and to the point.

Start gently, increase volume gradually, and keep your content engaging. An automated warm-up tool can help build reputation before you launch campaigns.

Yes. Experiment with different send times to catch your audience when they’re most receptive.

Email deliverability comes down to nine things: warming up your domain, using a professional ESP, personalizing your emails, keeping your list clean, optimizing for mobile, avoiding common pitfalls, setting up authentication, staying compliant, and prioritizing quality.

Get these right and your cold emails land in primary inboxes instead of spam folders.

The next step? Audit your current setup. Run a deliverability test, check your authentication records, verify your list, and watch your inbox placement over time.

If you want all of this in one place (warmup, authentication, inbox-placement testing, and real-time alerts), start a 14-day free trial of lemlist or book a demo to see how it works for your team.