Cold emailing remains one of the most powerful outreach strategies, but there’s a major challenge almost everyone faces: deliverability. The truth is, cold email isn’t dead, but most people’s deliverability might as well be. You’re not getting replies not because your copy or lead list is bad—it’s because your emails are landing in the spam folder instead of the primary inbox.
We’ve sent thousands of emails with consistent 5% reply rates, and in this guide, we’ll walk you through exactly how to fix your deliverability. From domain setup to email copy, sequence management, and metrics, we cover everything you need to know to ensure your cold emails land where they should—in the primary inbox.
1. Domains & Mailboxes: The Foundation of Deliverability
Deliverability starts with the right domain and mailbox setup. Here are key tips to get this right:
- Choose the Right Top-Level Domains (TLDs): Always buy secondary domains, not your primary business domain, to send cold emails. Opt for reputable TLDs like
.com or .net. For country-specific targeting, use localized TLDs like .co.uk or .de. Avoid cheap or low-reputation registrars like Namecheap, which can harm your deliverability. - Set Up Proper DNS Records: Implement DMARC, SPF, and DKIM records correctly. These authenticate your domain and prove to email service providers (ESPs) that you’re a legitimate sender. While you can do this manually, tools like Mailforge, Infraforge, and Warmforge automate this process, making setup easier and more reliable.
- Use Domain Forwarding or Masking: Forward your secondary domains to your primary domain, or better yet, use domain masking with SSL. This keeps your domain visible and prevents redirects, which ESPs view favorably, helping avoid spam filters.
- Manage Mailboxes and Sending Limits: Create 2-3 mailboxes per domain and limit sending to about 20 warm-up emails and 30 cold emails per mailbox daily. Avoid exceeding these limits unless you have private infrastructure with excellent reputation.
- Enable Mailbox Rotation: Use sending software that rotates mailboxes randomly across campaigns to distribute sending volume evenly. This prevents overloading any single mailbox and protects your domain reputation.
- Randomize Sending Times: Space out emails by 2-5 minutes per mailbox, avoiding mass blasts that raise spam flags.
- Conduct Regular Domain Health Checks: Monitor whether your domains appear on blacklists like Barracuda or Spamhaus. If blacklisted, retire those domains and create new ones. Also, check domain reputation and regularly perform mailbox placement tests to verify inbox placement.
- Warm Up Your Mailboxes: Warm up mailboxes for at least two weeks before sending cold emails and keep warm-up running continuously. Use a warm-up provider with spam features to maintain flawless reputation. Warmforge offers AI-powered warm-up that mimics human behavior to build trust with ESPs effectively.
2. Email Copy: Crafting Content That Lands and Converts
The content you send matters just as much as your technical setup. Here’s how to optimize your cold email copy:
- Send Plain Text Only: Avoid links, calendar invites, images, GIFs, videos, or attachments in your initial outreach emails. These elements hurt deliverability by triggering spam filters. You can introduce links or media in follow-ups once you’ve confirmed inbox placement.
- Disable Tracking Features: Turn off open rate and link click tracking. These use pixels that can negatively impact deliverability.
- Avoid Spam Trigger Words: Words like “free,” “sale,” “hundred percent off,” and “money” are red flags for ESPs. Use spam checkers to identify and remove these words or replace them with synonyms.
- Limit or Avoid Emojis: Emojis can appear unprofessional and may reduce deliverability. One smiley face max—if any.
- Use Spintax or AI Personalization: Ensure every email is unique by spinning your content or leveraging AI to personalize messages based on prospect data. Sending identical templates signals spam to ESPs and ruins your chances.
- Use Custom Variables: Personalize greetings and content with the recipient’s first name or company details to increase engagement.
- Don’t Mislead: Avoid clickbait or misleading subject lines or email content. For example, don’t use “Pizza Delivery” to lure opens if your offer is unrelated—that’s a guaranteed spam flag.
- Keep Subject Lines Short: Aim for four words or less to improve open rates and scan-ability. You can test longer lines, but shorter usually wins.
- Write Short, Scannable Emails: Keep email bodies between 20 to 70 words. Busy prospects won’t read long paragraphs. Make every word count.
- Run A/B Tests: Always experiment with subject lines, copy length, personalization styles, and CTA types to find what resonates best with your audience.
- Be Specific: Use tangible results in your copy. Instead of vague promises like “I’ll get you clients,” say “I’ll book 30 meetings in 2 weeks or you don’t pay.” Specificity builds trust and clarity.
- Use Soft Calls to Action (CTAs): Avoid hard CTAs like “Book a call.” Instead, start conversations with questions like “Is this relevant to you?” or “Can I send over some resources?” The goal is to engage, not pressure.
3. Sequence Management: Timing and Follow-Ups Done Right
Managing your email sequences properly is critical for maintaining deliverability and maximizing replies:
- Space Follow-Ups by 2-3 Days: Don’t flood inboxes. Give prospects time to respond.
- Limit Follow-Ups to 2-3 Messages: More follow-ups increase spam risk and reduce reply chances. If no response after three attempts, move on.
- Respect Do-Not-Contact (DNC) Requests: Immediately add anyone who asks not to be contacted to your DNC list. This prevents spam complaints and protects your reputation.
- Monitor Bounce Rates: Keep bounce rates below 1%, and never exceed 3%. High bounce rates signal poor list quality or domain issues. If bounce rate spikes, pause your campaign, validate your list, and fix problems before continuing.
- Remove Underperforming Mailboxes: If a mailbox repeatedly lands in spam, remove it from your infrastructure to protect the overall reputation. Replace it with new mailboxes and reduce sending volume temporarily.
- Validate Emails Before Sending: Always verify your email lists—even if purchased or claimed validated—to avoid sending to invalid or catch-all addresses that increase bounce rates.
- Use Multi-Language Sequences: If your audience is international, send emails in their native language. Personalized greetings in the prospect’s language dramatically increase reply rates.
- Match ESPs: Use Gmail mailboxes to reach Gmail inboxes and Outlook mailboxes for Outlook recipients. This ESP matching improves deliverability.
4. Metrics: What to Track and What to Aim For
Measuring your outreach success is essential, but some metrics matter more than others:
- Open Rate: Although we recommend disabling open rate tracking due to its impact on deliverability, if you do track it, aim for at least 70%. Lower rates indicate deliverability or subject line issues.
- Reply Rate: The industry average is 1-2%, but by following these best practices, you should aim for around 5%. This is achievable and reflects a well-optimized campaign.
- Positive Reply Rate: Of all replies, strive for at least 50% to be genuinely interested in your offer. Around 20% of replies should convert into booked calls or meaningful engagements.
Boost Your Cold Email Deliverability with Warmforge
Deliverability is a complex puzzle, but tools like Warmforge make it manageable. Warmforge is not just an email warm-up tool—it’s a complete email deliverability command center. It warms up your mailboxes by mimicking human behavior using AI, helping establish trust with ESPs naturally. You can monitor mailbox health, run placement tests to check inbox placement across providers, and keep your sender reputation flawless with continuous automated warm-up.
With Warmforge, you can:
- Warm up mailboxes with a single click, ensuring you’re ready to send cold emails without landing in spam.
- Monitor DNS and MX records, blacklist status, and mailbox reputations with Health Checks.
- Run monthly placement tests to see how your emails perform across Gmail, Outlook, and other ESPs.
- Keep your warm-up always on to maintain consistent deliverability and avoid sudden drops in reputation.
Start with a free warming slot and placement test today to take control of your cold email deliverability and maximize your outreach success.
Frequently Asked Questions
What is Warmforge and how does it work?
Warmforge is your go-to tool for email warm-up and deliverability management. It mimics human email interactions using AI to build trust with email providers, ensuring your mailboxes stay healthy and your emails reach the primary inbox.
Is there a free trial?
While mailbox slots need to be purchased to warm up mailboxes, you can sign up to explore Warmforge’s features for free and perform a free Placement Test to see deliverability in action.
How long does it take to properly warm up a mailbox?
We recommend warming up your mailbox for at least two weeks before sending cold emails and keeping Warmforge on continuously afterwards.
Do I have to keep Warmforge on at all times?
Yes. Turning Warmforge on and off irregularly can hurt your deliverability. Keeping it always on signals consistent sending behavior to ESPs.
How many placement tests do I need?
Placement tests send emails to different ESPs to check your inbox placement. At minimum, run one placement test per mailbox per month. More frequent tests can help you catch issues early and optimize your campaigns.
Will Warmforge work with my existing email tools?
Yes! Warmforge supports all Google Workspace and Outlook mailboxes and integrates easily with most email sending platforms, including Salesforge.
Conclusion
Cold email deliverability is the cornerstone of successful outreach. By carefully setting up your domains and mailboxes, crafting plain-text, personalized, and spam-free copy, managing sequences thoughtfully, and monitoring key metrics, you can consistently land in the primary inbox and achieve reply rates well above industry averages.
Leverage tools like Warmforge to automate warm-up, monitor your mailbox health, and perform placement tests. These steps will protect your sender reputation and maximize your cold email success in 2025 and beyond.
Remember, cold emailing isn’t dead—it just requires smart deliverability strategies to thrive.