Secondary domains are a smart way to protect your primary domain when running cold email campaigns. Sending cold emails directly from your main domain risks blacklisting, which can disrupt critical communications. Secondary domains act as a buffer, ensuring your primary domain remains secure while allowing you to scale outreach safely.
Key Takeaways:
getyourbrand.com).A secondary domain is an extra domain name you purchase to complement your primary domain. While your main domain handles essential business tasks like customer support emails, onboarding, and internal communication, secondary domains are specifically used for cold outreach efforts.
This separation is key. By keeping cold outreach activities on secondary domains, you reduce the risk of any issues - like spam complaints or deliverability problems - affecting your primary communication channels.
For instance, Smartlead.ai uses its main domain (smartlead.ai) for customer communications, while relying on secondary domains such as smartleadgrowth.info, smartleadinfo.co, and smarterleaderemails.co for cold email campaigns. Similarly, Pipl.ai safeguards its primary domain by using alternatives like usepiplai.com and getpiplai.com for outreach.
Understanding how secondary domains work lays the groundwork for exploring their key advantages.
One of the biggest advantages is protecting your reputation. Sending cold emails from your main domain can be risky - every bounce, spam report, or deliverability issue could harm your primary domain's standing. This could lead to critical customer emails ending up in spam folders, which is a nightmare for any business.
Secondary domains act as a buffer. If one of them gets flagged or blacklisted, your main domain stays unaffected, ensuring that vital communications like customer inquiries or support emails continue to reach inboxes without interruption.
Another important benefit is scaling your outreach efforts. Each secondary domain allows you to create additional email addresses, increasing your overall daily sending capacity. Instead of being restricted by the limits of a single domain, you can distribute your email campaigns across multiple domains, enabling higher volumes while staying within safe limits.
Better campaign organization is another perk. Assigning specific domains to different campaigns or audience segments makes it easier to track results, identify what works, and troubleshoot any deliverability issues without interfering with other campaigns.
Successfully managing secondary domains requires careful attention to mailbox limits and sending rules. The setup might seem simple, but it’s critical for maintaining good deliverability and staying off spam radars. A good rule of thumb is to limit each secondary domain to 2–3 email addresses. This keeps your operations looking natural to email providers.
When it comes to daily sending limits, start small - 30 to 50 emails per mailbox per day. New email addresses don’t have a sending history, so sending too many emails right away can trigger spam filters. Email providers like Gmail and Outlook are particularly vigilant with new accounts.
For example, if you need to send 1,000 emails daily, you’ll want to use about 7 secondary domains, each with 2–3 email addresses. This approach ensures you stay within safe limits while maintaining strong deliverability.
It’s also essential to gradually increase your email volume. Start with 10–20 emails per day for the first week, then slowly ramp up to around 50 emails per day per address over the next 2–4 weeks. Sticking to this gradual increase helps avoid spam filters and reduces the risk of your domain being blacklisted. Always reserve your primary domain for warm, essential communications, and keep it out of cold outreach activities.
Before diving into the technical details, take time to plan your secondary domains. Decide how many you’ll need, establish clear naming conventions, and organize everything upfront. This preparation will save you a lot of hassle down the road and set the stage for smooth technical configurations later.
When choosing names for your secondary domains, aim for something that ties back to your brand but still stands apart from your primary domain. One effective strategy is using brand variations, like adding prefixes such as get, try, use, go, or my. For instance, if your main domain is "acmecorp.com", your secondary options could include "getacmecorp.com", "tryacmecorp.io", or "useacmecorp.net."
Alternatively, you can incorporate keywords that highlight your business focus. A marketing agency, for example, might use domains like "acmegrowth.com", "acmemarketing.co", or "acmeleads.io." These variations keep your brand recognizable while clearly distinguishing outreach efforts from your main communications.
Domain extensions are more important than you might realize. Stick to well-established ones like .com, .net, .io, .co, and .org. These are seen as more trustworthy by both email providers and recipients, often leading to better deliverability rates. Avoid newer or less common extensions like .xyz or .click unless you’re targeting specific niches or regions.
Keep your domain names short and simple. Shorter names are less likely to be flagged as spam and are easier to manage.
Once you’ve decided on naming conventions, figure out how many domains and mailboxes you’ll need to meet your outreach goals.
Start by defining your daily email volume goals. Let’s say you want to send 1,000 emails per day. With each domain hosting 2–3 mailboxes and each mailbox sending about 50 emails daily, you’d need around 7–10 domains. This setup provides 14–30 mailboxes, giving you plenty of capacity while staying within safe sending limits. Always leave room for growth - don’t max out your capacity from day one.
Think about your future growth plans too. If you’re expecting to double your email volume within six months, it’s smarter to prepare now by setting up extra domains. Scaling later can be more time-consuming and disruptive.
You might also want to segment your campaigns. For example, separate domains can be used for different product lines, target demographics, or campaign types. This segmentation not only helps you track performance more effectively but also isolates potential deliverability issues to specific campaigns.
When it comes to providers, your choice depends on your needs. Traditional email platforms work well for general business communication, but specialized providers are better suited for cold outreach. Look for providers that offer automated DNS setup for critical records like DMARC, SPF, and DKIM. Manual setup for multiple domains can be a tedious process, but automated tools can handle this in minutes, saving you hours of work.
Providers that support multiple workspaces are especially helpful. They allow you to create separate environments for different teams, projects, or campaigns. This flexibility makes it easier to reassign domains or mailboxes as your needs evolve.
Cost is another key factor, especially when scaling. For instance, Google Workspace costs about $8.40 per mailbox per month, while platforms like Mailforge charge $2–$3 per mailbox. Over time, those savings can add up significantly.
"Operating in a high-growth startup environment requires speed, scalability, and operational efficiency. We needed to build an outbound motion that didn't break as we scaled - and Mailforge gave us that foundation." - Isabella L., Founder, Let's Fearlessly Grow
Compatibility with your email-sending software is also crucial. Make sure the provider you choose integrates seamlessly with your preferred cold email tools. This flexibility ensures you’re not locked into one system and can switch platforms as your needs change.
Setup time varies widely between providers. Traditional platforms often require manual configuration, which can take hours per domain. In contrast, specialized providers like Mailforge can provision domains and mailboxes in just minutes - a major advantage when managing dozens of domains.
"Procedures that usually took hours (setting DKIM, SPF, etc. records) for multiple domains, now take a few minutes. Mailforge is also cost-efficient since you spend per mailbox ~3 times less than with Gmail. The support team replies in minutes and is happy to sort out issues in a proactive manner!" - Danny Goff, Director of Sales, Propeller
Finally, consider the IP infrastructure your provider uses. Shared IP pools can improve deliverability by spreading your emails across multiple IP addresses, but this depends on the provider’s reputation management. High-quality shared pools often perform better than dedicated IPs with no sending history.
With your domains and providers planned out, you’re ready to move on to configuring and optimizing your secondary domains.
With your domain strategy in place, it's time to handle the technical setup - configuring DNS records, SSL certificates, and domain masking. These steps ensure your emails land in inboxes while safeguarding your primary business domain.
DNS records are the backbone of email delivery. Without proper authentication, email providers might flag your messages as suspicious or reject them altogether. To avoid this, you'll need to set up three key records: SPF, DKIM, and DMARC. These records establish trust for your secondary domains while keeping your primary domain secure.
v=spf1 include:_spf.google.com ~all. The ~all indicates a "soft fail" for unauthorized senders, which is suitable for cold email campaigns.
selector._domainkey.yourdomain.com.
v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com, to monitor performance without blocking legitimate emails.
Setting up these records manually across multiple domains can be tedious and prone to errors. Tools like Mailforge simplify this process, handling DNS configurations automatically and saving hours of work.
Once you've set up the records, propagation can take 24–48 hours. Use tools like MXToolbox or DNSChecker to verify everything is configured correctly. Only start sending emails once all records are valid across multiple DNS servers. After this, you can move on to securing your domains with SSL certificates.
SSL certificates are crucial for securing the connection between your domain and email recipients. Without them, email clients and spam filters may flag your domain, harming both trust and deliverability. SSL certificates also prevent security warnings that could scare off recipients.
Many domain registrars offer free SSL certificates through services like Let's Encrypt. However, managing SSL certificates across multiple domains can quickly become overwhelming. Certificates need to be renewed every 90 days, and any misstep in configuration could affect your email campaigns.
Automating SSL management eliminates these headaches. When your provider handles SSL certificates, you don’t need to worry about renewals or errors. This is especially important for cold email campaigns, where even minor technical issues can impact deliverability.
SSL certificates also secure tracking pixels and redirect links in your emails. Without SSL, recipients might see security alerts when clicking links, which can erode trust and lead to your domain being flagged. Once SSL is set up, the next step is configuring domain masking for branded tracking links.
Domain masking allows you to use your secondary domains for branded tracking links, replacing generic URLs like click.emailprovider.com/track123 with something more trustworthy, such as resources.yourcompany.com/whitepaper. This not only protects your primary domain but also boosts trust and engagement.
Branded links improve click-through rates because recipients are more likely to trust familiar domains. They also help maintain a consistent brand image across your email campaigns while reducing the chances of links being flagged as suspicious.
To set up domain masking, you'll need to configure CNAME records. For example, you might create a CNAME record for links.yourdomain.com that points to your email provider's tracking domain. This isolates tracking activities to your secondary domains, ensuring your primary domain remains unaffected if a secondary domain is flagged.
Some email platforms charge extra for custom tracking domains, and managing multiple domains can get tricky. Mailforge simplifies this by including SSL and domain masking for $2 per domain per month (or $6 per domain per year), making it an affordable option for scaling your campaigns.
Domain masking also strengthens email authentication. When your tracking links match your sending domain, it creates a consistency that spam filters recognize as legitimate. This alignment is becoming increasingly important as email providers enhance their filtering systems.
With your DNS records propagated, SSL certificates active, and domain masking in place, your secondary domains are ready for mailbox creation and warming. This solid groundwork ensures reliable email delivery as you expand your outreach efforts.
Once your secondary domains are ready, the next step is to set up and warm up your mailboxes. This process is crucial for maintaining strong deliverability as you scale your outreach efforts. Rushing through it can trigger spam filters and harm your sender reputation, so take it slow and steady.
A good rule of thumb is to use 3-5 mailboxes per domain. This spreads your email volume across multiple addresses, minimizing the risk of any single mailbox being flagged. If one mailbox encounters issues, the others can keep your outreach running smoothly.
When creating mailboxes, opt for professional, business-like names. Examples include sales@yourdomain.com, marketing@yourdomain.com, outreach@yourdomain.com, or business@yourdomain.com. Stay away from generic or suspicious names like noreply@ or random strings like abc123@, as these can raise red flags with spam filters.
Make sure to adjust your daily sending limits based on your email provider’s guidelines (covered earlier). Calculate your total sending capacity by factoring in the number of domains and mailboxes you’re using.
Platforms like Mailforge can simplify this process dramatically. With Mailforge, you can create hundreds of mailboxes across multiple domains in just minutes. It automates everything, from DNS configuration to mailbox setup, saving you hours of manual work.
Once your mailboxes are ready, the next step is to warm them up gradually to establish a strong sender reputation.
Warming up mailboxes is a process that takes about 2-3 weeks. Jumping straight into sending large volumes of emails can backfire, triggering spam filters and even getting your domains blacklisted.
Start by sending 30-50 emails per day per mailbox in the first week. Gradually increase this to 75-100 emails daily in week two. During this phase, focus on sending emails to recipients likely to engage - such as internal team members, existing contacts, or subscribers from your primary domain. The goal is to generate positive engagement signals, like opens and replies, which email providers use to evaluate sender quality.
Keep a close eye on metrics like open rates, reply rates, and spam folder placement. Tools such as Mail Tester or GlockApps can help you determine whether your emails are reaching inboxes or being flagged as spam.
Engagement is key. Automated warming tools that send emails between fake accounts might seem convenient, but they lack the authentic behavior patterns that modern spam filters look for. Instead, send meaningful content to real recipients who are likely to engage with your messages.
By week three, you should be reaching your target sending volume while maintaining steady engagement. If you notice a drop in open rates or an increase in spam placements, reduce your email volume and extend the warm-up period. It’s always better to take your time than to risk damaging your reputation.
Warmforge, an email deliverability platform, can automate this entire warming process. It gradually increases your sending volume while monitoring key metrics, ensuring your mailboxes build strong reputations without requiring constant manual adjustments.
A well-executed warm-up process lays the groundwork for effective and natural email sending patterns.
Maintaining a healthy sender reputation isn’t just about volume - it’s also about variety. Here’s how you can diversify your sending patterns:
The warm-up phase is all about discipline and patience. Properly warmed mailboxes with strong reputations will help you achieve high deliverability rates over the long term. While the initial setup takes time, the payoff is a solid foundation for successful email campaigns for months to come.
Once your domains are configured and mailboxes are warmed up, the next steps are all about keeping a close eye on performance and scaling your efforts strategically. The success of a cold email campaign often hinges on how well you track metrics and adapt your approach. Poor monitoring can quickly damage your sender reputation, while a careful strategy can set you up for long-term success.
Pay attention to critical metrics like bounce rates, spam placement, open rates, and reply rates. These numbers provide a clear picture of how your campaigns are performing and where adjustments might be needed:
Set up a reliable tracking system - whether that’s a simple spreadsheet or built-in analytics - to record daily metrics for each domain and mailbox. If a domain's performance starts to dip, reduce its sending volume by 50% and extend its warm-up period by another week. Regular weekly reviews will help you spot trends and make informed adjustments.
These insights will also guide your decisions when it’s time to scale up your infrastructure.
Scaling up should be done gradually and with careful planning. Expanding too quickly can overwhelm your processes and lead to mistakes that hurt deliverability.
Tools like Mailforge can make this process much easier. Instead of manually configuring DNS records and SSL certificates for every domain, platforms like Mailforge allow you to add hundreds of domains and mailboxes in just minutes. This frees up your time to focus on campaign strategy rather than infrastructure details.
As you scale, shift your attention to maintaining a strong sender reputation.
A solid sender reputation is essential, especially when managing multiple domains. Your overall reputation is tied to the health of your entire email setup, not just individual domains. Here’s how to keep it in good shape:
Before you kick off your cold email campaign, it's crucial to double-check that your secondary domains are configured properly. This step ensures your emails are delivered effectively and don't end up in spam folders.
Start by confirming that all technical settings are in place. Specifically, review your DNS records to ensure SPF, DKIM, and DMARC are correctly configured. Once these are set up, the next step is making sure your emails actually land in recipients' inboxes.
After verifying your configurations, test your email deliverability to ensure your messages bypass spam filters. Perform seed tests by sending emails to major providers like Gmail, Outlook, Yahoo, and Apple Mail. This will help confirm inbox placement. Additionally, leverage deliverability tools to spot any issues with sender reputation, email authentication, or the content of your emails before hitting "send".
Setting up secondary domains for cold email campaigns involves thoughtful planning, precise technical setup, and ongoing monitoring. The process begins with choosing the right domains and determining the number of mailboxes needed to match your sending volume. It's crucial to stay within the daily sending limits recommended by your email service provider. Configuring DNS records - SPF, DKIM, and DMARC - lays the groundwork for email authentication, while integrating SSL and using domain masking adds an extra layer of security and protects your brand’s reputation. Together, these steps help build trust with email providers and enhance your inbox placement.
A critical part of the process is mailbox warming. By slowly increasing your sending volume over several weeks, you allow your domains to establish a strong sender reputation with major email providers. Additionally, varying your email patterns and maintaining consistent engagement helps reinforce your credibility as a legitimate sender.
Once your sender reputation is established, ongoing performance monitoring becomes key to sustained success. Keep a close watch on metrics like open rates, reply rates, and spam complaints across all domains. If you notice any performance dips, analyze the data and adjust your approach promptly. When it’s time to scale, expanding methodically ensures your campaigns remain effective.
For those looking to simplify these tasks, tools like Mailforge can be a game changer. Mailforge automates DNS setup, SSL integration, and bulk domain management, making it easier to manage and scale multiple domains quickly. This is particularly beneficial for agencies juggling campaigns for multiple clients.
Ultimately, the success of your secondary domain setup depends on treating it as an ongoing process. Regular maintenance, vigilant monitoring, and careful scaling will ensure your cold email infrastructure continues to deliver strong results as your business grows.
Using secondary domains for cold email campaigns is a smart way to shield your primary domain from potential risks. Sending cold emails directly from your main domain can result in blacklisting, spam complaints, and harm to your sender reputation. These issues could interfere with your ability to send crucial emails reliably, including essential business communications.
By using a separate domain for cold outreach, you protect the credibility of your primary domain, improve email deliverability, and maintain trust with your recipients. This strategy ensures that your business operations and important communications remain unaffected by outreach-related challenges.
To get your secondary domains ready for email campaigns without triggering spam filters, start by sending emails in small, controlled batches to recipients who are likely to engage. Gradually increase the volume over time, allowing email providers to recognize and trust your domain.
It's also crucial to authenticate your emails using SPF, DKIM, and DMARC. These protocols confirm that you're a legitimate sender, which helps protect your reputation.
Keep an eye on your sender reputation and steer clear of using language that might be flagged as spam. By following these steps, you'll improve your chances of landing in inboxes rather than being sidelined in spam folders.
To effectively scale your cold email outreach while safeguarding your sender reputation, start small and build gradually. Begin by sending 10–20 emails per day per account and slowly increase that number over a 30-day period. This approach helps you avoid spam filters and ensures a smooth ramp-up.
Make sure your domain is properly authenticated with SPF, DKIM, and DMARC records - these are essential for improving email deliverability. To keep bounce rates low, verify email addresses before sending, and consider using automated warm-up tools to establish trust with email providers. Spreading your email volume across multiple domains and mailboxes is another smart way to minimize the chances of being flagged as spam.
If you're handling large-scale campaigns, tools like Mailforge can make your life easier. With features like automated DNS setup, SSL integration, and domain masking, these platforms simplify scaling while helping you maintain strong deliverability rates.