Can I use the same sending domain for my old and new ESPs at the same time?

Yes, you absolutely can use the same visible From domain with multiple ESPs simultaneously. However, you must configure different technical subdomains for each ESP's Envelope From (Return-Path) and DKIM authentication records. This prevents conflicts in your DNS settings, especially for SPF, and ensures proper authentication by both platforms.

Do I need to warm up a new IP address even if I'm using an old, established domain?

Yes, a warm-up period is necessary even if you're using an existing domain. While your domain itself has a reputation, the new ESP will be sending from new IP addresses. ISPs build reputation based on both domain and IP. A gradual ramp-up of sending volume on the new IPs is crucial to establish a positive IP reputation and avoid deliverability issues, such as landing on a blacklist or blocklist .

Which DNS records are most important during this transition?

The primary DNS records to consider are SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). Each ESP will require its own SPF record, often configured on a unique subdomain (e.g., mail.oldesp.yourdomain.com and mail.newesp.yourdomain.com). Similarly, DKIM typically involves CNAME records that point to your ESP's authentication servers, also often on unique subdomains. DMARC records should be in place on your primary sending domain to monitor authentication results from both ESPs.

What are the implications if my DMARC policy is set to 'p=reject'?

If your DMARC policy is set to 'p=reject', it means that emails failing SPF or DKIM alignment will be rejected by recipient servers. This can pose a risk during a migration if the new ESP's authentication isn't perfectly set up from day one. It's often recommended to temporarily change your DMARC policy to 'p=quarantine' or 'p=none' during the transition to allow monitoring and prevent delivery failures of legitimate emails, then revert to 'p=reject' once confidence in the new setup is established.

How do I transition to a new ESP while maintaining sends on my current platform using the same domain? - Technical - Email deliverability - Knowledge base

Transitioning to a new Email Service Provider (ESP) is often a necessary step for businesses looking to scale, improve features, or optimize costs. The real challenge comes when you need to maintain continuous email sending from your existing platform using the same domain, while simultaneously warming up and integrating with the new ESP. This process can seem daunting due to potential DNS conflicts and the critical need to preserve your sender reputation.

Many marketers worry about email deliverability dropping, or emails landing in spam folders during such a transition. The key is understanding the different types of domains involved in email sending and how to configure them correctly for a gradual, smooth migration. I'll guide you through the complexities of using a single domain across multiple ESPs and how to safeguard your email program.

Understanding domain roles in email

When we talk about 'the same domain' in email sending, it can refer to several different components of an email. It's crucial to distinguish between these to manage your transition effectively. Conflicting DNS records are a common concern, especially when trying to use the exact same subdomain for all purposes across two ESPs simultaneously.

For instance, the visible From domain, the one your recipients see in their inbox, can indeed remain consistent across both your old and new ESPs. This is vital for maintaining brand recognition and recipient trust. However, the technical backend domains are where careful configuration is needed. Laura Atkins of Word to the Wise provides excellent insights into these distinctions.

The Envelope From domain (also known as the Return-Path or Bounce domain) and the DKIM domain are typically managed by your ESP. These domains should be unique for each platform. For example, if your visible From domain is yourdomain.com, your old ESP might use bounces.oldesp.yourdomain.com for bounces, while your new ESP uses bounces.newesp.yourdomain.com. This approach allows each ESP to handle bounces and email authentication correctly without conflicts, which is crucial for overall email deliverability.

The primary reason for separate Envelope From and DKIM subdomains is that SPF (Sender Policy Framework) records are typically set for these specific subdomains. You can only have one SPF record per domain or subdomain. If both ESPs tried to use the exact same subdomain for their Envelope From, you'd end up with conflicting SPF records, which would cause authentication failures and seriously damage your domain reputation.

The challenge

Using a single subdomain (e.g., mail.yourdomain.com) for SPF and DKIM authentication across two different ESPs at the same time.

Maintaining a healthy sender reputation on a new, un-warmed IP address while still relying on your established platform for primary sending volume.

Dealing with a DMARC policy set to 'reject' on your primary domain, which can immediately cause delivery failures for misconfigured sends.

The solution

Utilize distinct subdomains for the Envelope From and DKIM records specific to each ESP. The visible From domain can remain the same. This ensures proper email authentication.

Implement a structured IP and domain warm-up strategy on the new ESP, gradually shifting volume while closely monitoring performance metrics.

If your DMARC is at reject, consider temporarily moving to 'quarantine' or 'none' for monitoring during the transition to mitigate risks. Alternatively, ensure DMARC alignment is achieved from day one with the new setup.

DNS configuration for dual sending

The foundational step for a dual-ESP setup is configuring DNS records correctly. Each ESP will provide specific DNS records for email authentication, including SPF and DKIM. SPF records specify which IP addresses are authorized to send mail on behalf of your domain. Since each ESP will send from its own set of IPs, they will require their own SPF entry.

However, you can only have one SPF record per domain or subdomain. This is why using separate subdomains for the Envelope From address for each ESP is essential. For example, old.yourdomain.com for your current ESP and new.yourdomain.com for the new one. This allows each subdomain to have its unique SPF record, preventing conflicts.

DKIM (DomainKeys Identified Mail) uses cryptographic signatures to verify the sender. Each ESP will provide its own DKIM key and hostname, which also need to be published as CNAME records under different subdomains. This setup ensures that both ESPs can properly authenticate emails originating from your brand, maintaining sender reputation.

A critical consideration is your DMARC policy. If your primary domain's DMARC policy is set to 'p=reject', any emails failing SPF or DKIM alignment will be rejected outright. During a transition, especially with a new ESP's configuration, there's a higher risk of authentication failures. It's often safer to temporarily switch your DMARC policy to 'p=quarantine' or 'p=none' to monitor results and ensure proper alignment before enforcing a 'reject' policy.

Example SPF records for two ESPsDNS

Host: old.yourdomain.com
Value: v=spf1 include:spf.oldesp.com -all

Host: new.yourdomain.com
Value: v=spf1 include:spf.newesp.com -all

This structured approach to DNS management is key. By using distinct subdomains for the technical aspects (Envelope From, DKIM) while maintaining a consistent visible From domain, you can effectively send from both ESPs without conflict. This allows for a smooth, phased migration that protects your sender reputation.

Phased migration and reputation management

Even if you're using the same visible From domain, a new ESP means new sending IP addresses. Internet Service Providers (ISPs) build reputation based on IP addresses and domains. A new set of IPs needs to be warmed up gradually to build trust. This involves starting with low volumes to highly engaged subscribers and slowly increasing volume over time. Ignoring this can lead to emails landing in spam or even IP blocklists (or blacklists).

Your migration strategy should involve a phased transition. Start sending only critical or highly engaged segments through the new ESP while maintaining your larger, less engaged lists on the old platform. This allows you to monitor deliverability and make adjustments as needed. Over time, you can gradually shift more volume to the new ESP. Mailjet offers a useful guide on ESP migration best practices.

Throughout this process, closely monitor your deliverability metrics from both ESPs. Pay attention to bounce rates, complaint rates, open rates, and click-through rates. Look for any unusual spikes or drops, particularly on the new ESP. Many ESPs provide basic deliverability dashboards, but for deeper insights, you might need external monitoring tools or Google Postmaster Tools.

Consistency is paramount during the transition. Try to keep your sending volume, frequency, and content consistent on both platforms as you gradually shift. Avoid drastic changes that could signal suspicious activity to ISPs. This consistent behavior, combined with proper authentication, will help maintain your sender reputation and ensure a smooth migration.

Key practices for smooth ESP transition

Subdomains for authentication: Use distinct subdomains for each ESP's Envelope From and DKIM records to prevent DNS conflicts.
Gradual warm-up: Start slowly with the new ESP, sending to your most engaged segments first, then gradually increasing volume.
Monitor performance: Keep a close eye on deliverability metrics from both platforms throughout the transition period.
Consistent sending: Maintain consistent volume and content quality to reassure ISPs.

Summary of a smooth transition

Successfully transitioning to a new ESP while maintaining sends on your current platform using the same domain is absolutely achievable. It requires a clear understanding of email protocols and careful DNS management, particularly concerning subdomains for technical sending aspects.

By planning a gradual migration, strategically warming up your new infrastructure, and diligently monitoring your performance, you can ensure your email program continues to thrive without interruption. Prioritize email authentication, monitor your blocklist (or blacklist) status, and adjust your DMARC policy as needed. This meticulous approach will pave the way for a seamless ESP transition.

Views from the trenches

Best practices

Always use unique subdomains for the Envelope From address for each ESP to avoid SPF conflicts.

Ensure DKIM records are properly configured for each ESP's unique sending subdomain.

Implement a gradual warm-up strategy for new IPs on the new ESP, starting with highly engaged users.

Monitor deliverability metrics (bounces, complaints, opens, clicks) closely on both platforms.

Consider adjusting your DMARC policy to 'quarantine' or 'none' during the transition if you're on 'reject'.

Common pitfalls

Attempting to use the exact same subdomain for SPF and DKIM on multiple ESPs, causing authentication failures.

Shifting all email volume to a new ESP too quickly, leading to IP blocklisting and poor inbox placement.

Not monitoring deliverability metrics during the transition, missing early warning signs of issues.

Ignoring the implications of a DMARC p=reject policy on potentially misaligned emails.

Failing to notify your current ESP of the gradual reduction in volume, which can impact their IP reputation.

Expert tips

Map out all existing DNS records and sending domains before starting the migration.

Communicate clearly with both your old and new ESPs about your phased migration plan.

Test email authentication thoroughly using tools to ensure proper setup on both platforms.

Segment your audience by engagement to prioritize sending to your most active users on the new ESP during warm-up.

Be prepared to revert or adjust quickly if deliverability issues arise during the transition.

Expert view

Expert from Email Geeks says the main conflicting record will be the MX record, and its switch timing depends on the transition plan. The new ESP should assist with this.

March 22, 2021 - Email Geeks

Expert view

Expert from Email Geeks advises that you must have different subdomains in the envelope from address so that each ESP can handle bounces correctly.

March 22, 2021 - Email Geeks