The right ESP migration takes days, not months. Here's your complete roadmap to switching platforms without disrupting performance or losing momentum.

Thinking about switching email service providers? We get it—a migration can feel overwhelming, especially when you're juggling campaigns, busy maintaining good deliverability, and trying to avoid any disruption to your email program.

But here's the thing, moving to a new ESP doesn't have to be complicated or risky. With the right approach (and the right partner), you can make the switch smoothly and start seeing better results fast.

Whether you need access to better features and support, or need to improve your email deliverability and revenue, this guide will walk you through everything you need to know. We'll cover what to look for in a new ESP, how to plan and execute your migration, and how to protect your email performance throughout the process.

Key takeaways 

• An ESP migration doesn't have to be slow or disruptive; with the right approach, you can complete it quickly without any headaches 
• Your biggest priority during migration is protecting your sender reputation and email deliverability
• The best migrations happen when you choose a platform built for growth and a partner who supports you through the entire process
• Done right, switching ESPs isn't just a platform change, it's an opportunity to improve performance and unlock new capabilities

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What is an ESP migration?

ESP migration is the process of switching from one Email Service Provider (ESP) to another, transferring your email marketing program to a new platform. Brands often migrate to consolidate channels like email and SMS into a unified solution with centralized data management.

Key Components of the Migration Process

A typical ESP migration involves creating a custom migration plan based on your current email list and previous email campaigns. The process usually takes about two weeks and includes the following. 

• IP Address Warming: Your IP address changes from your current ESP to the new platform, and emails are sent to subscribers at a gradually increasing schedule to build sender reputation
• List Migration: Exporting your subscriber list from your current ESP and uploading it to the new platform, including opted-out subscribers to ensure they remain unsubscribed
• Integration Setup: Setting up connections with your current tools and platforms to ensure continuity

The goal is to maintain email deliverability and sender reputation while transitioning to the new platform without disrupting your marketing campaigns.

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Signs it might be time to switch ESPs 

If you're reading this, chances are you're already feeling the limitations of your current email platform. Here are some common signs it's time to make a move:

• Your ESP lacks the tools you need. You don't have access to advanced automation and segmentation capabilities to personalize campaigns and maximize revenue.
• Your deliverability needs a boost. Emails aren't consistently reaching inboxes, and your performance is suffering as a result.
• Support is lacking. You're dealing with long wait times, limited expertise, or a lack of strategic guidance from your provider.
• You're managing email and SMS separately. Coordinating campaigns across two platforms requires too much manual work, and you want a more seamless multi-channel experience.
• You've outgrown your platform. Your current ESP can't keep up with your growing subscriber list or evolving business needs.

If any of these sound familiar, it's worth exploring your options. The good news? Switching doesn't have to be disruptive—with the right preparation and partner, you can make the transition smoothly.

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Step-by-step ESP migration checklist

So how do you make that happen? Here's your roadmap.

A successful migration happens in three phases: preparing your current program, executing the transition, and monitoring performance post-launch. Here's everything you need to do to make the switch smoothly.

Phase 1: Pre-migration prep

Before you start moving anything over, take time to clean up your existing program and get organized. This prep work will make the actual migration faster and set you up for better performance on your new platform.

• Build your migration team
  Identify everyone who needs to be involved—both internal team members and any external vendors or consultants. Make sure stakeholders know the migration is happening and understand the timeline.
• Run a re-engagement campaign
  Send a campaign to win back inactive subscribers before you migrate. This helps you see who's still engaged with your emails and who should be removed from your list.
• Clean your subscriber list
  Remove inactive, unresponsive, and invalid email addresses. Migrating a clean list improves your deliverability and engagement rates from day one—and if your new ESP charges based on list size, you'll save money too.
• Organize your subscribers
  Segment your list based on engagement level, preferences, and behaviors. Having this structure in place pre-migration makes it easier to personalize and target your messaging once you're up and running.
• Document your current performance
  Record your key metrics—open rates, click-through rates, conversion rates, and revenue. You'll need these benchmarks to compare performance before and after the migration.
• Audit your campaigns and automations
  Review all your active email campaigns and journeys. Decide which ones are still effective and should be migrated, and which ones are outdated or underperforming and can be left behind. This is a good opportunity to refresh underperforming content.
• List out your integrations
  Make a record of all the third-party tools and services currently connected to your ESP. You'll need to reconnect these on your new platform.
• Set up your domain authentication
  Coordinate with your new ESP to set up your domain authentication (SPF, DKIM, and DMARC records). We'll cover why this matters in the deliverability section below.

Phase 2: During migration

This is where the actual transfer happens. Your new ESP should handle most of the heavy lifting, but there are a few things to stay on top of.

• Transfer your subscriber list
  Import your cleaned and segmented email list to your new platform. Double-check that all data fields mapped correctly and no subscribers were lost in the transfer.
• Recreate your email templates
  Set up your email templates and designs in the new platform. If your new ESP has a design team, this is a good time to consult them for optimization tips.
• Rebuild your automations and journeys
  Recreate your campaigns, triggered emails, and customer journeys. Pay close attention to triggers, timing, and segmentation rules to make sure everything fires correctly.
• Reconnect your integrations
  Set up all your third-party tools and services again—CRM, eCommerce platform, analytics tools, and any other apps that connect to your ESP.
• Warm up your IPs
  If you're using new IP addresses, you'll need to warm them up gradually. Start by sending to your most engaged subscribers in small batches, then slowly increase volume over 2-3 weeks. Skipping or rushing this step can hurt your deliverability. (See the deliverability section below for a detailed warming schedule.)
• Run parallel testing
  Keep your old ESP running while you test the new one. Send test campaigns to small segments and compare performance between platforms. This helps you catch any issues before fully committing to the switch.
• Don't turn off your old ESP yet
  Keep triggers and automations running on your old platform until you're 100% ready to go live with the new one. This prevents any gaps in customer communication.

Phase 3: Post-migration monitoring

You've made the switch—now it's time to make sure everything is working as expected and your performance stays strong.

• Verify your subscriber list
  Confirm your entire list transferred correctly and no data was lost or corrupted during the migration.
• Test everything thoroughly
  Check that all email templates render correctly across devices and email clients. Test sign-up forms, transactional emails, triggered automations, and any interactive elements to make sure they're working properly.
• Update website and app connections
  Make sure all links, APIs, and integrations connecting your new ESP to your website or apps are functioning. If these aren't set up correctly, your sign-up forms and automations won't work.
• Monitor deliverability closely
  Monitor deliverability closely - Keep a close eye on bounce rates, spam complaints, open rates, and click rates during your first few weeks on the new platform. (For specific thresholds and what to watch for, see the deliverability section below.)
• Get familiar with reporting tools
  Spend time learning how to build reports and measure performance in your new platform. The sooner you're comfortable with analytics, the faster you can spot opportunities and make data-driven decisions.
• Train your team
  Make sure everyone who'll be using the new ESP has platform access and has completed any onboarding or training. Share resources like help docs, tutorials, and best practices so your team can hit the ground running.
• Compare performance to your benchmarks
  After a few weeks, compare your current metrics to the benchmarks you documented pre-migration. This helps you understand how the switch impacted performance and where you might need to optimize.

Now that you have the full roadmap, let's dive deeper into one of the most critical aspects of migration: protecting your deliverability.

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Protecting your deliverability during the switch 

One of the biggest concerns when migrating ESPs is maintaining your sender reputation and making sure your emails continue landing in inboxes. The good news? With the right approach, and the right partner, you can protect your deliverability throughout the transition.

Why deliverability matters during migration

When you switch ESPs, you're often sending from new IP addresses and potentially new domains. Internet service providers (ISPs) like Gmail, Yahoo, and Outlook don't automatically trust these new sending sources—they need to see consistent, positive engagement before they'll reliably deliver your emails to inboxes.

If you rush the process or skip key steps, you risk your emails being flagged as spam, which can hurt your sender reputation and take months to recover from.

Set up your email authentication

Before you send a single email from your new ESP, you need to prove you're a legitimate sender. This means setting up proper email authentication:

• SPF (Sender Policy Framework) tells ISPs which mail servers are authorized to send emails on behalf of your domain.
• DKIM (DomainKeys Identified Mail) adds a digital signature to your emails so ISPs can verify they haven't been tampered with in transit.
• DMARC (Domain-based Message Authentication, Reporting & Conformance) tells ISPs what to do if an email fails SPF or DKIM checks.

Your new ESP should walk you through setting up these DNS records. It typically involves adding a few lines of code to your domain's DNS settings. And here's an important tip: use a dedicated sending domain (like mail.yourbrand.com) rather than a shared one. This gives you more control over your sender reputation.

Clean your list before migrating

As we mentioned in the checklist, cleaning your list before migration is critical. ISPs track bounce rates and engagement levels—if you suddenly start sending to a list full of dead addresses or unengaged subscribers, they'll flag your emails as unwanted.

The real risk isn't bringing inactive subscribers to your new platform—it's accidentally emailing them. When you migrate, it's easy to lose track of who was suppressed in your old ESP. That's why list cleaning before migration is so important: you focus on your engaged audience and ensure those inactive addresses are properly marked as suppressed in your new system from day one.

Before you migrate:

• Remove email addresses that have bounced or are invalid
• Make sure any suppressed profiles from your old ESP are tagged as suppressed in your new platform so you don't accidentally re-engage them
• Consider suppressing subscribers who haven't opened or clicked in 6-12 months (or run a re-engagement campaign first to give them one last chance)
• Segment your list so you can prioritize your most engaged subscribers when you start sending

Warm up your IPs gradually

If your new ESP uses different IP addresses than your old one, you can't just flip a switch and start sending at full volume. You need to warm up those IPs by gradually increasing your send volume over time.

Here's what a typical IP warming schedule looks like.

• Week 1: Start by sending to your most engaged subscribers only—people who've opened or clicked recently. Send to a small batch (a few hundred to a few thousand, depending on your list size).
• Week 2: Gradually increase volume each day. If you started with 500 sends on Day 1, you might send to 1,000 on Day 2, 2,500 on Day 3, and so on.
• Week 3-4: Continue scaling up until you're sending at your normal volume to your full list.

The key is to show ISPs consistent positive engagement. If people are opening and clicking your emails (and not marking them as spam), ISPs learn to trust your new sending infrastructure.

Your ESP should provide guidance on the right warming schedule for your list size. Some platforms handle this automatically, while others require you to manage it manually. At Attentive, we partner closely with you on everything from authentication setup, to your warmup strategy and more, so you feel supported every step of the way.

Monitor your metrics closely

During the first few weeks on your new platform, keep a close eye on these deliverability indicators:

• Bounce rate: A sudden spike could mean your list wasn't cleaned properly or there's an authentication issue.
• Spam complaint rate: If people are marking your emails as spam, ISPs will take notice. This should stay below 0.1%.
• Open and click rates: Compare these to your pre-migration benchmarks. A significant drop could indicate deliverability issues.
• Unsubscribe rate: A spike in unsubscribes after migration could signal that your messaging or frequency isn't resonating with your audience, or that you're reaching subscribers who weren't properly suppressed.

If you notice any red flags, address them immediately. The faster you catch and fix deliverability issues, the less damage they'll do to your sender reputation.

Work with your ESP's deliverability team

The best ESPs have dedicated deliverability teams that monitor your performance and proactively address issues. During migration, lean on this expertise. They should be:

• Reviewing your authentication setup
• Monitoring your IP warming progress
• Watching for any signs of deliverability problems
• Managing relationships with ISPs on your behalf
• Providing guidance if something goes wrong

At Attentive, we believe that protecting your email deliverability is a collaborative effort between you and our team. With a wealth of combined experience and a staggering 8 trillion emails sent, our in-house experts—hailing from the best ESPs in the industry—work tirelessly to ensure that your messages reach the inbox every time.

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What to look for in your new ESP

Beyond deliverability, there are several other factors that should influence your choice of ESP. Here's what to prioritize as you evaluate your options.

1. Advanced automation and segmentation

To run an effective email program, you need a platform that lets you engage the right customers, with the right messages, at the right time. Look for advanced automation features that allow you to create and send personalized triggered emails based on subscriber behavior—like browse and cart abandonment reminders, targeted product recommendations, and post-purchase follow-ups.

But automation is only as good as your ability to identify and reach the right people. Your ESP should have strong identity tools that help you recognize more website visitors and trigger more emails to the right individuals. Better identification means more triggered sends, which translates to more revenue.

2. Scalability and reliability

You shouldn't have to migrate your email program more than once. Choose a platform that can grow with you as you scale your business and subscriber list, with a provider that's constantly innovating to meet your evolving needs.

And scalability only works if the platform is reliable. Look for an ESP with a powerful server infrastructure that can handle high send volumes and ensure prompt delivery—no matter how big your list gets. This is especially critical during high-traffic moments like Black Friday/Cyber Monday, when you're sending more emails than usual. Before making a decision, ask potential providers about their uptime and any outages during peak shopping periods.

3. An intuitive, easy-to-use platform

Your ESP shouldn't feel like rocket science. Look for a platform with an intuitive interface that makes everything from designing emails to analyzing results straightforward—whether you're a seasoned marketer or new to email. 

Here's what that looks like in practice.

• Customizable templates you can make your own
  Not every email marketer is a designer, and that's fine. Your ESP should have a library of templates based on industry best practices, plus a drag-and-drop editor that makes it easy to create high-performing emails with all the right elements. Bonus points if you can save your own templates and content as you build out your program.
• Flexible reporting that helps you make better decisions
  To improve your email strategy, you need to regularly analyze what's working and what's not. Look for an ESP that gives you access to detailed insights and metrics directly within the platform—including cross-channel reporting, individual subscriber data, and performance snapshots. You want to be able to filter and drill down into your data to identify trends and opportunities.
• Resources to help you learn and grow
  There's always a learning curve with a new platform. The right ESP won't just have a team to help you get up to speed—they'll also provide plenty of self-serve resources like a help center, blog posts, and case studies so you can become an expert on your own timeline.

4. Platform-native AI tools

AI has transformed how marketers work, helping automate time-consuming tasks and drive better results. Look for ESPs that offer platform-native AI tools—not just integrations with third-party AI products—so you can streamline your workflow without leaving your platform.

The best AI features generate high-performing subject lines, email copy, and images with minimal effort. Even better if the platform uses machine learning to help you optimize elements like A/B testing and real-time retargeting across channels.

5. List cleaning services

When you migrate to a new platform, you don't want to bring cold subscribers and invalid email addresses with you—especially if your payment plan is based on list size. Look for an ESP that provides list cleaning services to help you remove unengaged and incorrect addresses. This improves your sender reputation and overall email performance from day one.

6. Multi-channel coordination

85% of shoppers who subscribe to a brand's SMS program also sign up for email. That means you need to be able to easily coordinate touchpoints across multiple channels within a single customer journey.

You can choose an ESP that integrates well with your SMS platform—or you can combine email and SMS within a single solution. Having all your data in one place means you can use each channel's strengths to your advantage, with less manual work and a better experience for your customers.

7. Hands-on support throughout migration and beyond

Migration can be time-consuming and stressful, particularly if you've dealt with lackluster support in the past. Look for a provider that will guide you through the entire migration process—and stick around after you launch.

The best ESPs make transferring your email program quick and straightforward, so you can start sending and driving revenue as soon as possible. And their support teams should be available post-migration to answer questions and help you optimize your program as you grow.

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Why brands choose Attentive

Now that you know what to look for in an ESP and how to execute a successful migration, here's how Attentive stacks up—and why brands trust us to handle their email programs.

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Ready to Make the Move?

Migrating to a new ESP is a big decision, but it doesn't have to be a stressful one. With proper planning, the right checklist, and a partner who's invested in your success, you can make the switch smoothly—and start seeing better results right away.

Here's what to remember:

• Clean your list and organize your data before you migrate
• Protect your deliverability by setting up proper authentication and warming your IPs gradually
• Test everything thoroughly before going live
• Monitor your performance closely in the first few weeks
• Work with an ESP that provides hands-on support throughout the entire process

The right email platform should do more than just send messages. It should help you identify more subscribers, automate smarter, deliver consistently, and coordinate seamlessly across channels. Most importantly, it should come with a team that's as committed to your success as you are.

If you're ready to explore what a migration to Attentive could look like for your brand, we'd love to chat. Our team will walk you through the process, answer your questions, and show you how we can help you get more out of your email program.

Learn more about Attentive Email