How ESP Matching Boosts Deliverability for AI SDRs

When AI SDRs send cold emails, deliverability often depends on how well the sender’s email provider aligns with the recipient’s. That's where ESP matching comes in. This method improves inbox placement by routing emails through the same email service provider (ESP) as the recipient’s. For example, emails to Gmail users are sent via Gmail, while those to Microsoft 365 users are routed through Outlook. This approach increases trust, reduces filtering, and strengthens sender reputation.

Here’s what you should know:

• Why it works: Email providers like Gmail and Microsoft 365 trust emails sent within their own ecosystems more than those from external platforms.
• How it’s done: Tools like Primeforge dynamically route emails based on the recipient’s domain, using Google Workspace, Microsoft 365, or backup options like Mailforge.
• Benefits: Higher inbox placement rates, fewer bounces, and better sender reputation.

How Primeforge Powers AI SDR Email Infrastructure

Primeforge offers a dynamic email infrastructure tailored for AI SDRs, designed to work across multiple email service providers (ESPs). Instead of tying you to one ESP, Primeforge smartly routes emails through the most suitable provider for each recipient. This reduces the risk of overloading any single provider and ensures better inbox placement. It’s a system that forms the backbone of effective AI SDR campaigns.

Sending from Multiple ESPs with AI SDRs

Primeforge supports AI SDRs like Agent Frank by distributing email sends across a network of ESPs, including Google Workspace, Microsoft 365, Mailforge, and Infraforge. This distribution happens automatically, based on the recipient's email provider and domain type.

Here’s how it works: when Agent Frank identifies a prospect with a Gmail address, the email is sent through a Google Workspace mailbox within Primeforge. If the next prospect uses an Outlook or Microsoft 365 account, the email is routed through a Microsoft 365 mailbox. For less common email providers, the system can use Mailforge (shared infrastructure) or Infraforge (private infrastructure).

This approach minimizes the load on any single provider, spreading email volume across multiple platforms to maintain reputation. Emails are also sent through their native ecosystems whenever possible, improving deliverability. The routing happens in real time, with Agent Frank’s system analyzing the recipient’s domain and choosing the best mailbox automatically - no manual effort required.

What You Need to Use Primeforge

To take advantage of Primeforge’s multi-ESP functionality, you’ll need to meet a few key requirements. These ensure your emails are properly authenticated and maintain strong deliverability.

1. Domain Setup
You’ll need dedicated domains specifically for cold outreach. Primeforge supports a variety of domain extensions, with pricing based on the TLD. For example, five ".com" domains cost $70 per year. These outreach domains should be separate from your primary business domain to protect its reputation.

2. Automated DNS Configuration
Primeforge simplifies domain authentication by automatically setting up SPF, DKIM, and DMARC records. This eliminates the hassle of manually configuring these protocols for each mailbox. The system also supports bulk DNS updates, which is especially helpful when managing multiple domains and mailboxes.

3. Mailbox Slots
To get started, you’ll need at least 10 mailbox slots. Pricing begins at $45 per month for 10 slots (monthly billing) or $38 per month (billed annually). The number of slots you require will depend on your sending volume and the ESPs you want to use. For effective ESP matching, you’ll want a mix of Google Workspace, Microsoft 365, and possibly Mailforge or Infraforge mailboxes.

4. U.S.-Based IP Addresses
All Primeforge mailboxes use IP addresses located in the United States. This improves deliverability for North American recipients, as emails sent from unexpected geographic locations are more likely to be flagged by email providers.

Primeforge also includes additional features like mailbox profile pictures, multiple workspaces for organizing campaigns, and API access for custom integrations. It’s compatible with any email-sending software but integrates seamlessly with other tools in The Forge Stack, such as Salesforge (where Agent Frank operates), Warmforge (for email warmup), and Leadsforge (for lead generation).

Note: While Primeforge provides the email infrastructure, each tool in The Forge Stack requires a separate subscription. You can use Primeforge mailboxes with external platforms, but its native integration with Salesforge fully automates ESP matching for AI SDRs. Together, these components optimize deliverability and ensure effective outreach across diverse recipient domains.

Setting Up ESP Matching in Primeforge

Once your Primeforge mailboxes are ready, the next step is to configure ESP matching. This setup ensures emails are routed intelligently by connecting your mailboxes and defining routing rules that determine which ESP handles each email. All of this happens at the workspace level in Primeforge, giving you full control over how your AI SDR balances email volume across providers.

Connecting Mailboxes and Configuring Routing Logic

To start, connect your Google Workspace and Microsoft 365 mailboxes directly through the Primeforge dashboard. The platform supports both providers natively, making the setup straightforward. Once connected, these mailboxes become part of your sending pool.

In the workspace settings, add and authenticate your mailboxes. Primeforge automatically verifies DNS records like SPF, DKIM, and DMARC to ensure proper configuration. If you’re using Mailforge or Infraforge mailboxes, they’re already provisioned within Primeforge and will appear in your pool instantly.

After connecting your mailboxes, you’ll need to set up routing logic. Primeforge uses recipient domain detection to determine the right ESP for each email. There are two routing options available:

• Workspace-level routing: This applies the same rules across all campaigns within a workspace, ideal for consistent outreach to a specific audience - like enterprise companies using Microsoft 365.
• Campaign-level routing: This allows customization for individual campaigns, making it perfect for managing outreach to different audience segments simultaneously.

When Agent Frank prepares to send an email, Primeforge analyzes the recipient’s email domain. For example, if the domain is "gmail.com" or another Google-hosted domain, the email is routed through a Google Workspace mailbox. Similarly, emails to "outlook.com", "hotmail.com", or corporate domains using Microsoft 365 are routed through a Microsoft 365 mailbox. For domains that don’t match either, the system defaults to Mailforge or Infraforge mailboxes based on your configuration.

To ensure uninterrupted sending, you can also set fallback logic. For instance, if your Google Workspace mailboxes hit capacity or become temporarily unavailable, Primeforge can reroute Gmail-bound emails through an alternate mailbox pool.

These routing settings allow you to fine-tune email delivery for optimal performance.

Setting Up Routing Rules for Improved Delivery

Routing rules give you detailed control over how emails are distributed. You can assign specific mailbox pools to recipient providers and configure mailbox rotation to ensure even distribution.

To create a routing rule, define the recipient criteria, such as their ESP (Google, Microsoft, or others), geographic location, or audience type. For example, you might set a rule like: “For Microsoft 365 recipients in the United States, use Microsoft 365 mailboxes from Pool A.”

Geographic targeting is especially useful for international outreach. For instance, Primeforge’s U.S.-based IPs help maintain trust and consistency with North American recipients. If you’re targeting prospects in other regions, you can prioritize a mailbox pool that better aligns with their location.

Mailbox rotation is another key feature, evenly spreading email volume across your pool to avoid overloading any single mailbox. You can configure rotation to either favor mailboxes with higher sender reputations or distribute sends equally. This careful routing is a cornerstone of Primeforge’s strategy for improving deliverability.

Additionally, you can create audience-specific rules based on factors like company size or industry. For example, if you’re targeting large enterprises that primarily use Microsoft 365, you can route those emails through Microsoft 365 mailboxes. Meanwhile, emails to smaller companies using Google Workspace can be routed accordingly. Agent Frank can even pull company data from your CRM or lead database to apply these rules automatically.

Once your routing rules are in place, Primeforge applies them to all outgoing emails. Before each send, Agent Frank checks the rules and selects the appropriate mailbox based on your logic.

Need to tweak your rules mid-campaign? No problem. Adjustments take effect immediately, and Primeforge will apply the updated logic to all future emails. This flexibility lets you quickly address any deliverability challenges without disrupting ongoing sends.

After configuring your rules, keep a close eye on performance metrics to ensure your setup is delivering the results you need.

How ESP Matching Improves Inbox Placement

Building on the idea of precise email routing, ESP matching not only optimizes delivery paths but also bolsters your sender reputation. This approach ensures that emails land in the inbox by sending Agent Frank's messages through the recipient's familiar ESP, using trusted authentication protocols.

The advantage of ESP matching lies in minimizing delivery friction. For example, Gmail’s spam filters are designed to handle emails from Google Workspace differently than those from other services. Similarly, Microsoft’s security systems prioritize messages originating from Microsoft 365 mailboxes. Aligning with the recipient’s email provider creates a trusted pathway for delivery.

Routing Emails Based on Recipient ESP

The concept behind ESP matching is straightforward: send emails using the provider your recipient trusts most. For Gmail users, this means routing emails through Google Workspace mailboxes. For corporate users on Microsoft 365, sending through Outlook (Microsoft 365) mailboxes typically yields better results. When matching isn’t feasible - like with private domains or high-volume campaigns - Mailforge and Infraforge mailboxes provide reliable alternatives.

Using native infrastructures strengthens authentication. Gmail and Microsoft security systems favor emails routed through their platforms, ensuring inbox placement by consistently validating protocols like SPF, DKIM, and DMARC.

This is especially beneficial for small and mid-sized businesses using Google Workspace with custom domains. Routing emails through Google’s infrastructure helps maintain your message’s integrity and authenticity.

Similarly, Microsoft 365 mailboxes are essential for reaching enterprise users. Many large corporations rely on Microsoft 365, and their security systems are designed to trust emails sent from within the same environment. By leveraging Microsoft 365 for corporate outreach, you reduce the risk of triggering unnecessary security checks or spam filters.

For domains outside Google or Microsoft ecosystems, or when sending volumes exceed the capacity of your main pools, Mailforge and Infraforge mailboxes serve as dependable backups. These alternatives ensure consistent delivery and provide overflow capacity when needed.

The routing process is automated based on predefined rules. Agent Frank analyzes each recipient’s domain, identifies their ESP, and selects the appropriate mailbox from your pool. For example, in a campaign targeting 1,000 prospects, emails might be divided among Google Workspace, Microsoft 365, and Mailforge, depending on the recipients’ email environments.

This tailored routing lays the groundwork for Primeforge’s additional steps to improve deliverability.

How Primeforge Strengthens Deliverability Signals

Primeforge builds on precise routing by enhancing your sender reputation with strategic infrastructure choices. A key advantage is the use of U.S.-based IP addresses. By assigning mailboxes to IPs located in the U.S., Primeforge helps avoid unnecessary scrutiny from spam filters and supports a stable sender reputation through consistent geographic origins.

Another critical feature is automated DNS authentication. Primeforge handles the setup of SPF, DKIM, and DMARC as soon as you link your mailboxes. This automation eliminates common setup errors and ensures your emails are properly authenticated, which is essential for maintaining trust with major providers like Gmail and Microsoft.

Balanced distribution across multiple providers is also vital. Instead of relying on a single ESP - which can lead to clustering issues or jeopardize your operation if one mailbox develops a poor reputation - Primeforge spreads email volume across Google Workspace, Microsoft 365, Mailforge, and Infraforge. This diversification mirrors the natural sending behavior of human sales reps, reducing risks and strengthening your sender reputation.

Tracking Deliverability Results

Measuring the impact of ESP matching requires a structured approach to data collection and analysis. By tracking clear metrics, you can determine whether ESP matching improves inbox placement and overall email performance. This section wraps up our exploration of how Primeforge's ESP matching optimizes email deliverability for AI SDRs.

The first step is to set up a measurement framework before diving into ESP matching. Start by gathering baseline performance data from your current email setup. Once ESP-based routing is in place, compare the new results to these benchmarks. This comparison will reveal how aligning your sending infrastructure with recipient email providers enhances your email campaigns.

Setting Baselines and Monitoring Performance

Begin by collecting deliverability metrics over a two-week period before enabling ESP matching. This timeframe balances capturing enough data to identify trends while allowing for quick implementation of improvements.

Focus on key metrics:

• Inbox placement rate: This measures how many emails land in the inbox rather than spam or promotional folders. For example, if Agent Frank’s inbox placement rate falls below 85%, it signals potential issues that ESP matching can address.
• Bounce rates: Separate hard bounces from soft bounces. Healthy campaigns should keep hard bounces below 2% and soft bounces under 5%. Higher rates often point to authentication or reputation issues that ESP matching can help resolve.
• Spam complaint rate: Even a 0.1% complaint rate can harm your sender reputation. Both Gmail and Microsoft 365 use complaint rates as critical filtering signals, so keeping this number close to zero is essential.

Break down these metrics by recipient ESP. For instance, emails sent to Gmail users may perform differently than those sent to Microsoft 365 accounts. You might discover that Gmail achieves an 88% inbox placement rate, while Microsoft 365 lags at 72%. These differences highlight where ESP matching can make the biggest impact.

Additionally, track open rates and reply rates as secondary indicators. While these metrics depend on content and targeting, they provide helpful context. A sudden drop in open rates, for example, can signal emerging deliverability issues.

Once ESP matching is active, implement daily monitoring. Keep a close eye on ESP-specific performance and adjust routing if you notice any declines.

With these baseline metrics in hand, you’ll be ready to evaluate the tangible benefits of ESP matching.

Comparing Results Before and After ESP Matching

The true value of ESP matching becomes clear when you compare key metrics before and after implementation. Here's an example of how the numbers might shift:

The most noticeable gains often occur with Microsoft 365 recipients, where inbox placement can improve by 15-25 percentage points. Corporate environments tend to have stricter security filters, which favor emails sent from Microsoft’s infrastructure. Gmail, while less strict, still shows improvements of 8-15 percentage points due to its preference for properly authenticated emails.

Reductions in bounce rates are another key benefit. ESP matching can lower hard bounces by 60-75% because authentication protocols work more effectively when using native infrastructure. This improvement has a snowball effect: fewer bounces lead to a better sender reputation, which further boosts deliverability.

ESP matching also stabilizes performance across campaigns. Before implementation, you might see one campaign hit 85% inbox placement while another drops to 65%. Afterward, performance becomes more consistent, making it easier to optimize and predict outcomes.

Monitor these metrics for 30 days after implementation. The first week often shows the most dramatic improvements as authentication signals strengthen. By weeks two and three, sender reputation solidifies, and by week four, you should see stable, elevated performance levels.

Lastly, ensure balanced routing across your ESPs. A well-tuned system typically distributes emails as follows: 40-50% through Google Workspace, 30-40% through Microsoft 365, and 10-20% through Mailforge or Infraforge for overflow and niche domains. Significant deviations might indicate routing issues that require adjustment.

For a controlled rollout, consider running A/B tests. Send 500 emails using your current single-ESP setup and another 500 with ESP matching. Comparing the results will provide clear evidence of improvement while minimizing risks during the transition.

Conclusion

ESP matching has changed the game for how AI SDRs manage email infrastructure. Instead of sticking with one provider, this method syncs your sending system with the recipient's environment. The result? Better inbox placement, a stronger sender reputation, and more reliable campaign performance.

Companies using ESP matching through Primeforge have seen noticeable improvements in email delivery rates, especially for Microsoft 365 and Gmail users. On top of that, it tackles a long-standing cold outreach issue by aligning email authentication with what recipients expect, boosting overall deliverability.

Key Takeaways

Here’s why ESP matching stands out:

• It turns your email infrastructure into a strategic tool. AI SDRs like Agent Frank automatically route emails for top-notch deliverability with minimal oversight. All you need to do is connect your Primeforge mailboxes, set up routing based on recipient domains, and track performance to maintain steady delivery rates while strengthening your sender reputation.
• It offers three standout advantages for cold outreach. First, it slashes bounce rates by ensuring authentication protocols work seamlessly on their native platforms. Second, it stabilizes campaign performance, removing the unpredictability of relying on a single ESP. Third, it builds a solid, long-term sender reputation by adhering to email providers’ best practices.
• The technical setup matters, too. Primeforge’s infrastructure, featuring U.S.-based IPs, ensures trusted delivery. With support for platforms like Google Workspace, Microsoft 365, Mailforge, and Infraforge, you can route emails based on volume, recipient type, or campaign goals. This flexibility protects your sender reputation, even as your email volume grows.

For teams serious about cold outreach, ESP matching isn’t just a nice-to-have - it’s essential. It ensures your emails land in inboxes, not spam folders. By combining smart routing, proper authentication, and tailored infrastructure, you gain a lasting edge in deliverability. As email providers continue tightening their filters, this approach will only become more crucial for staying ahead.

With these strategies in place, Primeforge equips AI SDRs to consistently secure the inbox placement that drives results.

FAQs

How does ESP matching help AI SDRs like Agent Frank improve email deliverability?

Email deliverability gets a boost when the email service provider (ESP) matches the recipient's platform. For instance, emails sent to Gmail addresses are routed through Google Workspace, while those targeting Microsoft users are sent via Outlook or Microsoft 365. This setup enhances inbox placement by improving compatibility and building trust.

With Primeforge’s infrastructure, AI SDRs like Agent Frank can send emails using multiple ESPs instead of relying on a single provider. This approach helps avoid clustering, ensures steady performance, improves deliverability rates, and creates a more dependable outreach strategy.

What do I need to set up Primeforge's ESP matching for successful email campaigns?

To get Primeforge's ESP matching up and running smoothly, follow these steps:

• Set up Google Workspace or Microsoft 365 mailboxes through Primeforge. These mailboxes are the foundation for reliable email communication.
• Configure key email authentication records like DMARC, SPF, and DKIM. These records are crucial for securing your emails and building trust with recipients.
• Link your mailboxes to your sending platform, such as Salesforge, to streamline email delivery.

By completing these steps, you'll ensure better email deliverability and maximize the benefits of Primeforge's infrastructure for your campaigns.

What metrics should businesses track to measure the impact of ESP matching on email deliverability?

When evaluating how ESP matching influences email deliverability, businesses should pay close attention to a few critical metrics: delivery rate, bounce rate, spam complaint rate, and unsubscribe rate. These numbers reveal whether emails are successfully reaching recipients and how those recipients are responding.

Another essential factor to monitor is inbox placement - specifically, whether emails are landing in the main inbox or getting stuck in spam or promotions folders. By digging into these metrics, businesses can gain a clearer picture of how ESP matching impacts their email performance and boosts engagement.

Related Blog Posts

• How ESP Matching Improves Email Deliverability
• Common Spam Triggers in Microsoft 365 Emails
• DMARC Policy Impact on Email Deliverability
• The Power of Diversification: Why AI SDRs Need Multi-ESP Email Infrastructure