In today’s highly competitive sales and marketing landscape, email remains one of the most powerful tools for connecting with prospects, nurturing leads, and ultimately driving client growth. However, the challenge lies in ensuring that your cold emails actually reach the inbox and generate meaningful responses rather than getting lost in spam folders. This is where warmed-up emails and strategic deliverability practices come into play.
At Salesforge, we’ve spent years mastering the art and science of email deliverability, working with hundreds of clients worldwide to help them unlock the true potential of cold outreach. This comprehensive guide dives deep into the best practices and hacks for warming up your email infrastructure, crafting effective cold email campaigns, and scaling your outreach without sacrificing deliverability or reputation.
Before diving into the technicalities of warming up emails and advanced hacks, it’s essential to grasp the three core pillars that impact cold email success:
Daniel, a seasoned deliverability expert from Warmy, sums it up perfectly: “The world is shifting towards highly targeted cold emails where sending less, but better, yields more results. You get fewer deliverability issues and higher engagement.”
Scaling cold email outreach has evolved dramatically over the last few years. Gone are the days when you could blast thousands of emails from a single mailbox without consequence. Today’s major email providers like Gmail and Outlook impose strict volume limits and penalize senders who trigger spam filters or generate complaints.
One of the most pervasive myths in cold emailing is the “50 emails per inbox per day” rule. While this number has long been touted as a safe benchmark, the reality is far more nuanced. According to Daniel, “Gmail’s G Suite allows sending up to 2,000 emails per day per account, provided you behave as a good sender.”
This means that if your emails consistently generate positive engagement - clicks and replies - and maintain low spam complaints and bounce rates, you can safely scale well beyond 50 emails per mailbox. The key is to demonstrate to email providers that you are a responsible sender, which is exactly what warming up your domain and mailboxes helps achieve.
When scaling cold outreach, it’s critical not to overload your primary sending domain. Instead, use secondary or “burner” domains dedicated solely to cold outreach. This protects your main company domain from reputational damage in case things go wrong.
Salesforge recommends setting up multiple domains and mailboxes to distribute your sending volume. For example, if you have 10 mailboxes, rotate your emails so each mailbox sends a portion of your total volume. This mimics natural sending patterns and reduces the risk of triggering spam filters.
Daniel explains, “You want to send fewer emails per domain and connect fewer inboxes per domain to reduce risk. The four factors impacting deliverability are the message, mailbox, domain, and IP. Distributing volume carefully across these helps maintain a healthy sender reputation.”
Starting to send cold emails from a brand-new domain without warming it up is a recipe for disaster. While you can technically send emails immediately, your domain will likely end up in spam folders or blocked entirely after just a few days.
Warming up a domain involves gradually increasing your sending volume while generating positive engagement signals. This process builds trust with email providers and spam filters, showing them that your domain is legitimate and your emails are wanted.
“When you buy a new domain, it’s often listed on blocklists or unknown to email providers. If you start sending cold emails too fast, your domain’s reputation plummets, and your emails land in spam,” Daniel warns.
Daniel highlights an interesting insight: “We’ve seen a 7% lift in open and reply rates when warming up in the same language and topic as your cold emails, compared to warming up with unrelated content.”
At Salesforge and Mailforge, we integrate with powerful warming tools like Warmforge that connect directly to Google Postmaster and other deliverability data sources. This allows for smart, machine-learning-driven warm-up processes that identify and fix issues proactively rather than blindly sending emails back and forth.
Google Postmaster is a free tool that provides insights into your domain and IP reputation, spam rates, and other critical metrics. Using this data, Warmforge can tailor your warm-up and sending strategy to maximize deliverability.
To avoid spam filters that flag repetitive content, it’s essential to diversify your email copy. Spintax is a popular method that randomizes parts of your email—for example, greeting variations like “Hi,” “Hello,” or “Hey.”
But with advancements in AI, you can now generate truly unique emails at scale, creating personalized messages for every recipient. This significantly improves deliverability and engagement.
Before launching campaigns, use tools to scan your email copy for spammy words or excessive links that might trigger filters. Keeping your email simple, clean, and free of unnecessary links is a best practice that improves inbox placement.
Open rates are often touted as a key metric, but they are actually unreliable and can be misleading. Email clients may pre-load images or block tracking pixels, skewing data.
Daniel puts it bluntly: “Open rates are a fake metric. What really matters is your reply rate, demo bookings, or whatever your ultimate goal is. Open rates don’t tell you if your emails are effective.”
Instead of sending all your emails from one mailbox in rapid succession, distribute your sends across multiple mailboxes randomly. This simulates human behaviour and reduces the risk of being flagged for spam-like activity.
Matching your sending domain’s email service provider (ESP) to your recipient’s ESP has become a topic of interest. For example, sending emails from Gmail mailboxes to Gmail recipients and Outlook mailboxes to Outlook recipients.
While there is anecdotal evidence of better deliverability with ESP matching - especially given recent Outlook restrictions - there is no definitive data yet. It’s an area worth exploring, especially if you have a clear understanding of your target audience’s email providers.
Regularly check your domains against spam boards and blacklists to ensure your sending infrastructure remains clean. Warmforge offers tools to automate these checks, helping you catch and resolve issues before they impact your campaigns.
Limit your cold email sequences to a maximum of three emails. Research shows that the probability of receiving a reply drops significantly after the third email, while spam complaints tend to increase.
Instead of bombarding prospects with endless follow-ups, use your sending capacity to reach new leads or re-engage dormant contacts quarterly. Timing is crucial in cold outreach, and persistence beyond three emails often does more harm than good.
Your subject line and preview text are the first things a prospect sees, often determining whether your email gets opened. Keep subject lines short (ideally two words) and in lowercase to stand out in crowded inboxes.
Also, leverage preview text to create a pattern interrupt. Instead of the usual “Hi [Name],” try starting your email with an intriguing or unusual phrase to capture attention.
Focus on micro-conversions like getting a reply rather than directly pushing for meetings in your first email. Soft CTAs such as “Is this a priority for you?” invite engagement without pressure.
Hard CTAs asking for a meeting or demo can come later in your sequence once you’ve established interest. This approach respects prospects’ time and increases your chances of meaningful conversations.
Adding a P.S. at the end of your email offers another opportunity to provide value or a soft nudge. For example, sharing a deliverability checklist or a helpful resource can encourage replies and build goodwill.
Avoid overly complex HTML signatures with multiple images and links in your initial cold emails. Plain text or simple HTML signatures build trust and improve deliverability. Once a conversation starts, you can use richer signatures to reinforce credibility.
Spicing up follow-up emails with personalised memes, GIFs, or videos can increase reply rates, especially when targeting creative or sales-oriented audiences. Tools like vidu.io enable you to generate thousands of unique, programmatic GIFs to entertain and engage prospects.
However, gauge your audience carefully - this approach might not be suitable for more traditional industries like legal or finance.
Deliverability is an ongoing process that requires regular monitoring and adjustments. Use platforms like Warmforge to run weekly deliverability checks, track domain reputation, bounce rates, spam complaints, and engagement metrics.
For tech-savvy teams, APIs are available to automate these checks and integrate deliverability insights directly into your sales and marketing workflows.
One of the biggest risks in cold emailing is hitting spam traps -email addresses created specifically to catch spammers. These traps can be sophisticated, with fake LinkedIn profiles and realistic company information to lure unsuspecting senders.
Daniel warns, “Spam trap operators buy defunct company domains and create fake personas. If you hit these traps, your domain’s reputation can be destroyed, and your emails will end up blocked.”
The best defence is thorough email verification and list hygiene, combined with smart targeting and warming practices.
Finally, remember that email preferences vary widely by geography and industry. For example:
Always test and adapt your copy length, style, and frequency based on your target audience’s behaviour and feedback.
Warmed-up emails are the cornerstone of effective cold outreach and client growth. By investing time and resources into proper domain warming, mailbox rotation, targeted content, and ongoing deliverability monitoring, you can dramatically increase your chances of landing in your prospects’ inboxes and eliciting responses.
At Salesforge, Mailforge, and Warmforge, we’re passionate about helping businesses unlock the full potential of cold email outreach. Combining cutting-edge technology with proven best practices, we empower sales teams to scale smarter, not harder.
Remember these key takeaways:
With these strategies, your cold emails won’t just be sent - they’ll be read, and replied to, turning prospects into clients and unlocking sustainable growth.
To get started, check out a free Salesforge trial and sign up for Warmforge to get free email warm up for one domain + one free placement test per month.
