The Ultimate 2026 Cold Email Deliverability Checklist
Contents
If your cold emails are going to spam or just not getting replies, it’s probably not your fault. In 2026, landing in the primary inbox is harder than ever. AI-powered filters, stricter regulations, and crowded inboxes mean that even the best emails can silently vanish into the spam abyss.
But what if you had a simple, actionable checklist to ensure your emails always get seen? In this article, we’ll go over 16 ways you can improve your cold email deliverability before starting a cold email campaign.
16 Things to Do Before You Send Your Cold Email
Before you hit “send,” you have to check these 16 boxes:
1. Authenticate Your Domain
Before you send anything, you need to prove your identity. To Gmail and Outlook, an unauthenticated domain looks suspicious from the start. Without the right records, your emails carry no verified signature, and inbox providers treat that as a risk.
Authentication fixes this. It adds cryptographic proof that you are the real sender and gives receiving servers clear instructions on how to handle your mail. You set this up through three DNS records at your domain provider:
- Sender Policy Framework (SPF). This is a public record that specifies exactly which servers are allowed to send mail for your domain. It stops spoofing and blocks anyone trying to send fake messages that look like they came from you.
- DomainKeys Identified Mail (DKIM). It adds a unique digital signature to every message. This helps receiving servers confirm that the email wasn’t altered and truly originated from your domain.
- Domain-based Message Authentication, Reporting, and Conformance (DMARC). It tells inbox providers what to do if something fails, such as quarantine it, reject it, or let it through. It also gives you reports on suspicious activity.
A DMARC policy of p=reject is fast becoming the industry standard for trustworthy senders. Not having one, or having a weak p=none policy, is a red flag that can keep your emails out of the primary inbox, even if everything else is perfect.
You can use a free tool like MXToolbox’s Deliverability Test to check if all three records are published correctly. Just enter your domain, and it will give you a pass/fail for each.
2. Use a Dedicated Sending Domain
Cold email, by its nature, has a higher chance of triggering spam complaints or blocks. If you use your primary email for cold emails, that can harm the deliverability of all your company’s emails.
To reduce this risk, you could set up a dedicated subdomain for your cold emails. It builds a separate reputation that inbox providers evaluate independently from your main domain. Gmail and Outlook score both the root domain and any subdomains, so splitting them gives you a protective buffer.
Plus, with a subdomain in place, any negative signals like spam complaints, low opens, and low replies stay contained. Your main domain stays clean, and all your business emails continue to reach your primary inbox.
3. Warm up Your Domain/IP
How you send emails is just as important as what you send. Sudden, large bursts of email from a new or inactive domain are a major red flag for spam filters and AI, because this mimics bot behavior. A warm-up phase can solve this.
The problem is that doing it manually drains time and rarely creates a natural engagement pattern. But with an automated warm-up service like Mailshake’s Email Warm-up, you can handle the entire workflow.
Your warm-up tool will send messages from your address to a controlled network of real inboxes, generate authentic-looking replies, and pull any messages out of spam. This will train the AI filters to trust your domain over time.
Here’s what to do:
- For a new domain or IP. Start with a low initial volume of emails, like 10 to 20 per day, to a highly engaged list and gradually increase the volume over 4–8 weeks. This slowly introduces your sender identity to email providers as a legitimate source of mail.
- For established domains. Maintain a consistent daily sending volume that fits with your list size and historical engagement. Also, space your emails naturally throughout the day instead of blasting hundreds at once.
Pro tip: Keep an eye on Google Postmaster Tools and Microsoft SNDS each week. Their reputation dashboards tell you if your warm-up is actually moving the needle.
4. Verify Your Sender Reputation
Inbox providers look at signals around your domain’s infrastructure to assess credibility. Your DNS and SSL setup aren’t direct ranking factors, but problems here create doubt about your domain’s legitimacy, and that doubt hurts deliverability.
Your DNS controls how your domain routes traffic. Misconfigured or unstable DNS records can cause intermittent delivery failures and make your domain look poorly maintained. That alone can lower trust with receiving servers.
Your links matter too. Every URL in your email should lead to a site protected with a valid SSL certificate (the https:// prefix). Pointing users to an unsecured http:// page can be risky, damage trust, and suppress engagement, which is another indirect hit to reputation.
So, before launching any campaign, run a DNS lookup to confirm everything is configured and propagated. Then click every link in your sequence to confirm the destination loads over HTTPS with an active SSL certificate.
5. Source Leads Responsibly
Sending to purchased, scraped, or rented lists is the single fastest way to destroy your sender reputation. These lists are filled with invalid addresses, spam traps, and people who never agreed to hear from you, guaranteeing high bounce rates and spam complaints.
Instead, you should build a list based on implied permission. This doesn’t always mean someone explicitly opting in to your cold emails; it means their professional contact information was publicly shared in a context that aligns with your offer.
Some examples include emails listed on LinkedIn profiles, company websites, conference speaker pages, and industry directories. You can use tools like LinkedIn Sales Navigator to target by industry, job title, and technology used, or source attendees from an industry webinar.
6. Scrub for Invalid Addresses
Even with perfect lead sourcing, your list will contain typos, invalid addresses, and toxic spam traps. Sending to these addresses tells email providers you are a careless sender, which can directly harm your reputation and deliverability.
To avoid this, here’s what to do:
- Make list verification a non-negotiable, automated step before importing any list into your cold email platform.
- Do not rely on manual checks or basic syntax validation. The small cost per email is insignificant compared to the reputational cost of sending to invalid addresses.
- Clean your list before every major campaign to remove addresses that have gone inactive or become invalid since your last send.
You can also use email verification tools to check each address against domain health, syntax errors, and known disposable email providers.
7. Segment by Relevance
Email providers interpret low engagement, such as a lack of opens, clicks, or replies, as a sign that your content is unwanted. This tells their algorithms to start filtering your future emails away from the primary inbox.
To prevent this, you should implement a “sunset policy.” This is a pre-defined rule that automatically removes contacts from your cold email lists after a specific period of inactivity.
A common and effective rule is: If a contact has not opened or replied to any of your last five to seven emails over a six-month period, automatically remove them from your cold email cadence.
That keeps your list clean and your engagement metrics high, which are positive signals for modern spam filters.
8. Remove Unengaged Contacts
Keeping unengaged contacts in your list drags down your open and reply rates, two signals inbox providers watch closely. Low engagement tells Gmail and Outlook that your emails aren’t wanted, which increases the odds of future messages landing in spam.
Segmentation fixes this.
Instead of sending one generic message to everyone, you should divide your master list into smaller groups that share similar traits. This can help you tailor your message, your offer, and your value proposition to speak directly to the specific pains and goals of each segment.
You can segment your list using criteria like:
- Job title/function
- Company size/industry
- Technographic
- Geographic location
Once you’ve segmented, create a unique angle for your highest-value groups. This can increase your reply rates and tell email providers your content is wanted.
9. Optimize The “From” Field
The “From” field is the first thing a recipient sees, and it can also affect their decision to open or ignore your email. If it looks generic, automated, or suspicious, recipients will hesitate, and inbox providers will take it as a credibility signal.
This means you should be specific in your “From” field, use a real person’s name, and set up a clean, authenticated sending domain to establish trust immediately. This will create a human connection and reinforce that the message isn’t coming from a bulk marketing account.
Here’s what to do:
- Use a personal format like “Sarah from Company Z.”
- Avoid vague or automated labels such as “The Sales Team,” “Marketing,” or “Do-Not-Reply.”
- Send from your dedicated outreach domain, e.g., sarah@reach.companyz.com, so recipients and spam filters instantly recognize a verified, reputable sender.
10. Write a Spam-Trigger-Free Subject Line
Your subject line is the key to your email being opened. But it is also heavily weighted by spam filters. Using certain words and formatting flags your email as promotional or malicious, ensuring it’s filtered out before a recipient ever sees it.
Spam triggers include:
- Overly salesy language
- Excessive punctuation
- AllcCaps
These tactics might have worked in the past, but modern AI filters are trained to detect and penalize them. So, to avoid ending up in spam, you should keep your subject lines clear and write as you would speak, not like you’re a corporate drone.
11. Personalize Beyond the Name
Using your recipient’s first name is the bare minimum and no longer counts as personalization. To stand out and prove you’ve done your homework, you should include at least one line of genuine, research-based personalization in the body of your email.
This could include:
- Their role in relation to a recent company project or achievement
- A shared connection or mutual interest
- A piece of content they recently shared or engaged with
This shows that you see the recipient as more than just an entry on a list and that your message was meant specifically for them. It also increases the likelihood of engagement, which is a powerful positive signal to email providers.
12. Prioritize Plain Text and a Clean Layout
Heavy HTML, multiple images, and complex formatting are red flags for spam filters. They can also slow down load times and render poorly in certain email clients, leading to a poor recipient experience and immediate deletion.
A clean, text-heavy email is more likely to be delivered and also more likely to be read. It feels like a personal message from one professional to another, not a broadcast advertisement. So, you should:
- Compose your emails in plain text or use very minimal HTML.
- Avoid large header images, background colors, or multiple fonts.
- Use standard font sizes and colors, preferably black text.
If you have to include an image, keep it small and make sure it’s relevant. A good rule is a 95/5 text-to-image ratio. This reduces spam triggers and increases the chance your message will be engaged with.
13. Limit Your Links
Spam often contains numerous links to various destinations, so including multiple links in a cold email is a red flag for email providers. It also forces your recipient to decide where to click, which often means they click nowhere.
Remember: you want to guide the prospect toward one clear, logical next step. This means every element of your email should support this single objective. Here’s what to do:
- Include only one primary link in your initial cold email. This link should be directly tied to your call-to-action, such as a link to your calendar, a highly relevant case study, or your LinkedIn profile.
- Hyperlink a natural phrase like “Read the case study here” instead of using a raw URL or a generic “Click here.”
14. Include One Clear CTA
An email that asks for multiple things, like a reply, a link click, and a document review, will get none of them. A confused prospect does not take action. So, your call-to-action has to be clear and easy to fulfill, with minimal effort required from your recipient.
Here’s how to make sure your emails actually prompt recipients into action:
- Define the one primary goal of your email before you write it.
- Write your CTA around that goal. The highest-performing CTAs are often low-friction requests like “Does this make sense?” or “Reply with ‘yes’ if this is a priority this quarter.”
- Ensure your single CTA is prominently placed and supported by the entire body of your email. Every sentence should build a case for taking that one specific action.
15. Include an Unsubscribe Link
Providing a clear and functional unsubscribe mechanism is not just a legal requirement under laws like GDPR and CCPA; it is a critical deliverability best practice.
When a recipient can’t easily unsubscribe, their most likely alternative is to mark your email as spam. And a high spam complaint rate is one of the fastest ways to destroy your sender reputation.
A one-click unsubscribe process instantly removes the recipient from your list, which prevents future emails, protects your reputation, and keeps your list clean and engaged. Just make sure your unsubscribe link is clearly visible in the email body, not hidden in tiny text.
The process also has to be instant and should not require a login or a confirmation page. Making it easy to opt out is paradoxically one of the best ways to ensure your emails keep reaching the people who want them.
16. Manage Your Sending Volume and Cadence
Once your domain is warmed up, you need to protect that reputation through steady, human-like sending patterns. But maintaining this consistency across multiple inboxes, campaigns, and follow-up sequences is nearly impossible to track manually.
One slip, like an overloaded inbox, a campaign launching at the wrong time, or a spike caused by follow-up, can create deliverability issues that take weeks to repair.
To avoid that, you need a scheduling tool, such as Mailshake’s Sending Calendar, that gives you a clear view of your daily outgoing volume across every connected inbox. This scheduling tool will help you:
- See if one inbox is on track to send too many emails. If it is, you can shift volume across other inboxes before providers throttle your sending.
- Keep your daily sending at a reputation-safe level, even when follow-ups kick in automatically.
- Space emails across your chosen sending window so messages land at high-engagement times instead of hitting inboxes all at once.
- Ramp up gradually and never jump from 20 to 300 emails overnight, which can get a domain blocked.
- Full control over your sending rules, which means you can customize which days of the week emails go out, the exact time window messages should send, how spaced-out each message should be, and more
This helps you grow your outreach in a controlled, reputation-safe way, so every increase in volume strengthens your results instead of damaging your domain.
Final Thoughts
Deliverability isn’t a one-time fix. It’s an ongoing process of monitoring, testing, and improving. Our 16-point checklist is the system that walks you through this process. It moves you from being a sender who hopes emails get delivered to one who knows they will.
So, bookmark it and use it as your pre-flight checklist for every single campaign you launch. Because for each point you check off, you’re actively building a higher level of trust with email providers.
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