You can write the perfect cold email with a strong CTA, personalization, and a great offer, but none of it matters if your email never reaches the inbox.
That’s the reality most sales teams face.
With spam filters becoming more aggressive and email service providers (ESPs) tightening their security, ensuring your cold emails actually get delivered has become a challenge.
Whether you’re an SDR scaling outbound efforts or a marketer supporting pipeline goals, you need to get the technical foundations right.
Cold email deliverability isn’t just about writing better subject lines; it starts way before that, with how you set up your domains, email accounts, and sending infrastructure.
This post covers a complete cold email deliverability checklist, including technical setup, content guidelines, and sending behavior.
Follow it to improve inbox placement, avoid spam folders, and give your outbound strategy a real chance at success.
But before that, let’s quickly cover what email deliverability is and why it is so challenging in cold emails.
What Is Email Deliverability – and Why It’s a Challenge in Cold Outreach
Email deliverability refers to the ability of your emails to successfully reach a recipient’s inbox. It’s not just about whether the email is sent; it’s about where it lands: inbox, spam, or promotions.
In cold email outreach, deliverability becomes especially challenging because you’re contacting people who haven’t opted in. That means ESPs (like Gmail or Outlook) are more likely to scrutinize your messages.
They assess your sender reputation, technical setup, content quality, and recipient engagement before deciding whether to deliver the email and where to place it.
Cold emails also carry higher risks of being marked as spam, ignored, or bouncing if you’re not careful with list hygiene and sending behavior.
Even one mistake, like sending too many emails too fast or using a spam trigger word, can negatively impact your domain reputation.
That’s why optimizing deliverability is critical for outbound success.
Cold Email Deliverability Checklist
To improve cold email performance, you need more than just a great copy; you need the right technical setup, sending behavior, and list.
Here’s a checklist that will serve as a step-by-step guide to ensure your emails land in inboxes, not spam folders.
1. Set Up a Dedicated Sending Domain
Use a secondary domain specifically for cold email outreach instead of your company’s primary domain. It should look closely related to your brand (e.g., company.io → companyhq.io).
Why this matters:
This keeps your main domain’s reputation safe from potential spam complaints or blacklisting. It also allows you to scale outreach efforts while maintaining domain trust over time.
2. Configure Email Authentication Records (SPF, DKIM, DMARC)
Proper authentication builds trust with ESPs and helps them verify that your emails are legitimate.
- SPF tells receiving servers which IPs are authorized to send emails for your domain.
- DKIM attaches a digital signature to your messages to confirm authenticity.
- DMARC sets policies for how servers should handle emails that fail SPF or DKIM checks.
Why this matters:
Without these records, your emails are more likely to be flagged as suspicious and routed to spam folders or blocked entirely.
3. Warm Up Your Email Account Gradually
When using a new inbox, don’t start sending cold emails immediately. Warm up the account by sending and receiving emails over a few weeks.
How to do it:
- Start with 10 – 20 emails per day.
- Slowly increase the volume over time.
- Make sure you’re getting replies and engagement (opens, clicks).
Why this matters:
A warm sending history builds sender reputation, making providers more likely to deliver your emails to the primary inbox.
4. Set Up a Custom Tracking Domain
Instead of using the default tracking domain provided by your email platform, configure a custom one that aligns with your brand (e.g., track.companyhq.com).
Why this matters:
Default tracking domains are often shared among users and can carry poor reputations. A custom tracking domain gives you more control and avoids being affected by others’ sending behavior.
5. Monitor and Limit Daily Sending Volume
Each inbox should send a limited number of cold emails per day to avoid triggering spam filters.
Best practices:
- Start small – 20 to 30 emails per day for new inboxes.
- Don’t exceed 50 – 75 cold emails per inbox per day.
- Use multiple inboxes and domains if you need higher volumes.
Why this matters:
Excessive sending from one address is a red flag and can quickly damage your sender’s reputation.
6. Rotate Between Inboxes and IPs When Scaling
For high-volume sending, use multiple domains, inboxes, or rotating IPs to spread out the load.
Why this matters:
Rotating IPs reduces the risk of blacklisting and throttling by ESPs. It also allows you to continue sending even if one IP or domain gets temporarily flagged.
7. Avoid Spammy Language and Design in Emails
Your email content should be clean, concise, and free of language or formatting that could trigger spam filters.
Avoid:
- All caps or excessive punctuation (e.g., “!!!”).
- Words like “Buy now,” “Risk-free,” and “Limited time.”
- Too many links or images.
- Unnatural formatting, fonts, or bold text.
Why this matters:
Even technically well-configured emails can be flagged if the content looks suspicious or promotional.
8. Personalize Every Email You Send
Use custom fields to insert names, company details, or role-specific insights. But go beyond just basic merge tags.
How to do it:
- Reference recent company news or activity.
- Acknowledge a shared connection or challenge.
- Mention tools, software, or services the lead already uses.
Why this matters:
Highly personalized emails improve reply rates and reduce spam complaints, which positively influences your sender score.
9. Always Include an Unsubscribe Option
Provide a clear and easy way for recipients to opt out of future emails. This can be a one-click unsubscribe link or a simple sentence asking them to reply with “unsubscribe.”
Why this matters:
Unsubscribe links reduce the chance of your emails being marked as spam, and in some countries, they’re required for compliance (e.g., GDPR, CAN-SPAM).
10. Validate and Clean Your Email Lists
Before sending, always verify that your contacts’ email addresses are valid and active.
How to do it:
- Use an email verification service to check deliverability.
- Remove hard bounces and invalid addresses regularly.
- Avoid old, scraped, or unverified lists.
Why this matters:
High bounce rates damage your reputation and signal to ESPs that you’re sending to low-quality lists.
11. Monitor Sender Reputation and Blacklists
Check your domain and IP reputation regularly using tools like MX Toolbox, Google Postmaster Tools, or similar.
Why this matters:
If your sender reputation drops, or you end up on a blacklist, your emails will start going to spam or getting blocked. Early detection helps you take corrective action.
12. Track Key Engagement Metrics
Engagement is a core signal email providers use to decide inbox placement.
Monitor:
- Open rate: Aim for 40% or higher.
- Reply rate: 5 – 10% is healthy.
- Spam complaints: Keep as close to zero as possible.
- Bounce rate: Should not exceed 2%.
Why this matters:
Consistently low engagement tells ESPs your emails are irrelevant, which hurts your deliverability.
13. Send Emails at Logical Times and Intervals
Time your emails for business hours based on the recipient’s time zone, and don’t flood inboxes with too many follow-ups.
Best practices:
- Send between 9 AM and 4 PM local time.
- Wait 3 – 5 days between follow-ups.
- Limit sequence length to 3 – 4 emails.
Why this matters:
Sending at irregular hours or too frequently can lead to higher unsubscribe or spam complaint rates.
14. Regularly Audit Your Infrastructure and Lists
Maintain a recurring schedule to check on your cold email setup and database.
What to audit:
- DNS records (SPF, DKIM, DMARC)
- Bounce and complaint rates
- Domain and IP reputation
- List quality and engagement metrics
Why this matters:
Ongoing maintenance ensures long-term deliverability and avoids sudden drops in performance.
Winding-up
Cold email still works, but only if your emails actually reach the inbox. With spam filters and user expectations evolving, sales teams can’t afford to overlook deliverability.
It’s not a “nice to have”, it’s foundational.
Use this checklist before launching your next campaign. From domain setup and warm-up to content hygiene and engagement monitoring, every point contributes to inbox placement.
The goal isn’t just to send more emails, it’s to get more responses. And that starts with deliverability.