How to Scale Cold Emailing to 10k Emails/Month with No Risks

In the fast-paced world of outbound sales, mastering cold emailing is crucial for success. However, sending thousands of cold emails every month without risking your sender reputation or landing in spam folders is a complex challenge. This article dives deep into building an antifragile cold email infrastructure that enables you to scale your outreach effectively while maintaining high deliverability and engagement rates.

Drawing on insights from sales and cold email experts: Frank Sondors of Salesforge and Ilya Diponas of Growth Band, this guide covers everything from technical domain setup and email volume management to choosing the right email service providers and crafting the perfect outreach strategy. Whether you're a sales leader, founder, or marketer, this comprehensive approach will help you generate leads at scale with confidence.

Why Deliverability is the Foundation of Successful Cold Emailing

Before diving into advanced tactics like AI personalization or buyer intent signals, it's essential to understand that none of these strategies will matter if your emails never reach the inbox. Deliverability - the ability of your emails to bypass spam filters and land in the primary inbox - is the most fragile and critical aspect of cold emailing.

Deliverability challenges have intensified recently due to evolving email service provider (ESP) algorithms and anti-spam measures. For example, Google has recently restricted open tracking by flagging invisible tracking pixels, which has made traditional open rate metrics less reliable and even harmful to your sender reputation.

In this environment, focusing on deliverability means:

• Ensuring your technical email infrastructure is airtight
• Sending emails from trusted, properly configured domains and mailboxes
• Maintaining high engagement rates to avoid spam complaints
• Reducing bounce rates by using accurate contact data

Without these fundamentals, your personalized or AI-driven cold emails won’t be seen, let alone replied to.

Building an Antifragile Cold Email Infrastructure

The term “antifragile” refers to a system that doesn’t just withstand shocks but improves because of them. In the context of cold emailing, an antifragile infrastructure is one that can handle fluctuations in deliverability, provider restrictions, and recipient behavior without collapsing or losing effectiveness.

Key components of such an infrastructure include:

• Multiple domains and mailboxes: Avoid sending all cold emails from one domain or mailbox. Instead, spread your volume across several domains and mailboxes to diversify risk.
• Proper technical setup: Implement all necessary DNS records such as SPF, DKIM, DMARC, and MX to authenticate your emails and prove domain ownership.
• Warm-up processes: Gradually increase sending volume to build a positive sender reputation before scaling.
• Monitoring and maintenance: Regularly test inbox placement and track engagement metrics to detect and resolve deliverability issues swiftly.

This approach helps you avoid the catastrophic impact of a single domain or mailbox being blacklisted or marked as spam, ensuring your cold email campaigns remain sustainable.

The Importance of Domain and Mailbox Management

How many domains and mailboxes you need depends on your email volume goals and the sending limits of your chosen ESPs. For example, Google typically allows around 30 cold emails per mailbox per day. If you’re aiming to send 10,000 emails per month, you’ll need multiple mailboxes and domains to distribute this load.

Here’s a practical example based on a goal of generating 30 marketing qualified leads (MQLs) per month:

1. Assume a positive reply rate of 0.45% and a reply rate of 4.5%.
2. To get 30 MQLs, you need approximately 300 replies.
3. To achieve 300 replies with a 4.5% reply rate, you must send emails to about 6,600 contacts.
4. Considering follow-ups (usually 4), the total emails sent could reach around 26,000 per month.
5. With 30 emails per mailbox daily and 22 sending days per month, each mailbox can send approximately 660 emails monthly.
6. Therefore, you’d need roughly 40 mailboxes distributed over 10 to 20 domains (assuming 2-4 mailboxes per domain).

This example highlights why scaling cold email campaigns requires careful planning and a diversified infrastructure rather than relying on one domain or mailbox.

Technical Setup: The Backbone of Deliverability

Many cold email campaigns fail because of improper domain and mailbox configuration. Ensuring your domain's DNS records are correctly set up is non-negotiable for good deliverability. Key records include:

• SPF (Sender Policy Framework): Specifies which servers are authorized to send emails on behalf of your domain.
• DKIM (DomainKeys Identified Mail): Adds a digital signature to your emails to verify they weren’t altered.
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Tells receiving servers how to handle emails that fail SPF or DKIM checks.
• MX (Mail Exchange): Directs incoming emails to your mail server.

Setting these up correctly confirms to ESPs that you legitimately own the domain and mailbox, reducing the chances of your emails being flagged as spam.

Additionally, avoid using free Gmail accounts or aliases for cold emailing, as these are often flagged. Instead, use dedicated mailboxes on your owned domains designed specifically for cold outreach.

Choosing the Right Email Service Providers and Infrastructure

Not all email providers and sending infrastructures are created equal. Cold emailing at scale requires a multi-layered approach involving different ESPs and sending methods to diversify risk and maximize deliverability.

Google Workspace vs Microsoft 365 vs SMTP Providers

Both Google and Microsoft offer shared IP pools for sending emails, meaning your emails share IP addresses with other senders. While Google tends to have a more forgiving reputation system by recognizing your domain's identity, Microsoft’s reputation is more tied to the IP address used.

A best practice is to use a combination of Google Workspace mailboxes, Microsoft 365 mailboxes, and dedicated SMTP providers. This diversified setup allows you to send emails from multiple infrastructures, reducing the risk of blacklisting or deliverability issues affecting your entire campaign.

For example, if your target market includes enterprises, Microsoft mailboxes may be more effective since many large companies use Microsoft-based email systems. For small to medium businesses, Google mailboxes often perform better.

Why Avoid Using Marketing Automation Tools for Cold Email

Many marketers mistakenly use tools like Mailchimp, SendGrid, or HubSpot for cold emailing. However, these platforms are designed for opt-in marketing and transactional emails, not cold outreach.

Using these tools for cold emails risks getting your account banned and your deliverability damaged. Cold emailing requires specialized tools that support multi-domain, multi-mailbox sending, warm-up processes, and deliverability monitoring.

Crafting Cold Emails That Avoid Spam Filters

Aside from technical setup and infrastructure, the content of your cold emails significantly impacts deliverability. Here are key considerations:

• Keep your emails simple and clean: Avoid heavy HTML, excessive colours, or embedded images which can trigger spam filters.
• Use proper links: Avoid suspicious or shortened URLs that look spammy.
• Limit bounce rates: Use verified and up-to-date contact lists to prevent emails from bouncing, as high bounce rates damage your reputation.
• Recipient engagement: Encourage positive engagement by sending relevant, personalized emails to the right audience.
• Include unsubscribe options: This can reduce spam complaints and improve deliverability. Consider adding unsubscribe links in email headers or mixing unsubscribe text naturally within the email body.

Personalization and Targeting

While deliverability is the foundation, relevance drives engagement. Target the right buyer personas, industries, and job roles. Tailor your messaging to address specific pain points rather than pitching your product directly in the first email.

Test different value propositions and messaging angles to find what resonates best with your audience. For example, longer, detailed emails may perform better in markets like Germany, where recipients prefer more information upfront.

Scaling Cold Email Outreach Safely and Effectively

How Many Emails Should You Send?

Instead of asking “How many emails should I send?”, start with “How many leads do I want to generate?” Then work backwards using your conversion metrics.

For instance, if your goal is 30 MQLs per month and your reply to MQL conversion rate is 10%, you need 300 replies. If your reply rate is 4.5%, that means emailing approximately 6,600 contacts. Accounting for follow-ups, you might send 26,000 emails monthly.

Knowing this, you can calculate the number of mailboxes and domains needed based on daily sending limits per mailbox.

Horizontal Scaling with Multiple Domains and Mailboxes

Scaling horizontally means distributing your email volume across many domains and mailboxes to avoid overloading any single sending address. This prevents rapid deterioration of sender reputation and reduces the risk of blacklisting.

For example, sending 200 cold emails per day from one mailbox is no longer feasible without risking spam folder placement. Instead, spread those 200 emails across 5 mailboxes sending 40 emails each.

Domain Age and Quality Matter

Older domains (2-3 years) tend to have better deliverability than brand-new ones, but new domains can still perform well if warmed up properly. Avoid cheap or suspicious TLDs like .xyz, which are often associated with spammers and have poor reputation.

Dot com domains remain the gold standard due to user familiarity and trust. Local TLDs (e.g., .fr for France) can be effective when targeting specific geographies.

Warm-up Pools and Domain Rotation

Warming up a domain means gradually increasing email sending volume to build a positive sender reputation. Join reputable warm-up pools that maintain clean sending practices and avoid bouncing emails.

Domains typically “burn” (lose reputation) within 4-6 months, so keep a reserve of warmed-up domains ready to rotate in and replace burned ones quickly to avoid downtime.

Monitoring and Maintaining Your Email Infrastructure

Continuous monitoring is critical to detect deliverability issues early and respond effectively. Some best practices include:

• Use placement testing tools (e.g., Warmforge, Mailreach) to check if your emails land in primary inboxes or spam folders.
• Monitor bounce rates, spam complaint rates, and reply rates regularly.
• Use Google Postmaster Tools to track your domain’s spam complaint rates and reputation.
• Analyze engagement metrics and adjust sending volume or content accordingly.

Regular health checks help you identify when a domain or mailbox is “burned” so you can replace it before it damages your overall campaign performance.

Best Practices for Follow-ups and Multithreading

Follow-ups are essential to maximize reply rates. Typically, sending 3-4 follow-up emails per contact increases chances of a response.

However, avoid sending follow-ups with tracking pixels or heavy HTML in the first email, as these can harm deliverability. Tracking on follow-ups is generally safer.

Multithreading - contacting multiple stakeholders within the same company through email, LinkedIn, or phone -increases conversion rates and reduces dependence on a single touchpoint.

Legal Considerations and GDPR

Compliance with data protection laws like GDPR and CCPA is important, though legislation varies by country and changes frequently. Best practices include:

• Allowing clear and easy opt-out or unsubscribe options
• Respecting opt-out requests promptly
• Sending relevant and respectful messages without excessive frequency
• Consulting legal experts for region-specific advice

Being a good sender not only protects your reputation but also builds trust with prospects.

Optimizing Your Cold Email Campaigns Through Testing

Testing different messaging hypotheses is key to discovering what resonates with your audience. This goes beyond simple A/B tests of subject lines or email copy. Instead, focus on:

• Identifying pain points and challenges your prospect faces
• Testing different value propositions and angles
• Segmenting by buyer persona and ICP for targeted messaging
• Scaling winners and iterating quickly

Ensure your tests are statistically significant by running campaigns with sufficient volume (e.g., 1,000 leads per variant) to avoid misleading results.

Conclusion: The Four Pillars of Cold Email Success

Successful cold email outreach rests on four key pillars:

1. The right email tool and execution strategy: Use specialized cold email platforms that support multi-domain, multi-mailbox setups with deliverability features.
2. Robust infrastructure: Build and maintain an antifragile email sending infrastructure with proper domain setup, warm-up, and monitoring.
3. Compelling and relevant copy: Craft personalized, problem-focused messages that engage your target audience.
4. Accurate and clean data: Send emails to the right contacts using verified and segmented lists.

If any of these pillars are weak, your campaigns will struggle. Strengthen each area to scale your cold emailing to 10,000+ emails per month with minimal risks and maximum impact.

For those looking to build or optimize their cold email infrastructure, leveraging expert tools and consulting services can accelerate success and avoid costly mistakes. Remember, cold emailing today requires the same rigor and investment as running paid ad campaigns - but with the right approach, it remains one of the most cost-effective channels for outbound lead generation.