…and make sure that your ESP migration is aligned with your annual event lifecycle
So your business is ready to migrate and upgrade email marketing ESP. Your current platform (is it Mailchimp? đ) is not working for you and your event/s anymore.
Your reasons for switching email marketing platforms could be many, budget, scale, functionalities, tech connections, or simple usability challenges.
So now youâre on a journey to pick your new ESP and start your migration. Youâve come to the right place!
This article will guide you through this process exactly. Starting with ESP research and how to approach choosing a new one, how to prep your migration so nothing breaks and your deliverability stays healthy, and where in your annual event cycle to get started. That last one is really important.
“Maria helped us migrate our mailing list from Mailchimp. She has done an amazing job in setting up our welcome journey for both our company newsletter signup and also our conference (Lean Agile London). Maria quickly understood our needs and set about delivering. Our email marketing has never been in better shape.” – Jean-Paul Bayley, Actineo Consulting & Lean Agile London
Know before you start your ESP migration journey
Migration is one of the highest-risk moves you can make with your email marketing. You’re making a significant change to your sending infrastructure, and inbox providers don’t like change.
You donât want to damage your domain reputation, push your emails into spam, and undo months of work and risk not getting the sales you need for the next event because of it.
Done right, it sets you up for better performance long-term.
Litmus puts a proper ESP migration at 3â6 months. (Litmus)
âBallpark how long you think it will take⌠then double it. It will always take more time, effort, and stakeholders than you think.â – Kisha Anderson
Luckily, your annual event lifecycle is perfectly set up for this.
How to choose your new ESP
I believe that choosing the ESP for your business and your event email marketing comes down to three things: your budget, the functions and features you want/need your new software to do, and the tech it connects to that makes your work easier.
Tech
Start with the thing thatâs the least flexible: your tech stack.
Having all your software speak to each other seamlessly, without extra third-party tools, means youâll spend less time setting things up, youâll pay for fewer tools, youâll have to troubleshoot fewer things, and you can have higher levels of trust in that your data is correct.
Functions/features
Once youâve established a list of ESPs that support your tech stack in a way that you like, move on to looking at functions/features and price.
Begin by listing all that works and doesnât work in your current ESP. Make a dream wishlist of what you ideally want it to do. And then start looking at feature lists online.
Different ESPs, annoyingly, talk about the same things using different language, so knowing what you want beforehand will help. Take your time to explore, set up trial accounts, and have sales conversations with reps.
Price & functions trade-off
This will narrow down your selection to the final shortlist, where you compare price and functions trade-offs.
Truly understand if the tool is the right fit for your business, your events, your workflows, and your audience’s needs before you decide if the ÂŁ50/m or ÂŁ100/m price points are right for you.
From there, make a call and make sure you are making a long-term commitment. You do not want to be changing ESPs a year or even three from now.
Credit: The following migration plan is adapted from Beth OâMalleyâs article, How to Successfully Migrate ESPs (and What your Boss Needs to Know). The structure, steps, and logic are hers, I’ve restated them in my language before adding the annual event lifecycle details. For the deeper technical detail, especially per-provider warmup and how to brief your boss, read Beth’s original. Beth is the expert in this area, follow her.
Let the migration begin! ButâŚ
Before you touch anything: run a deliverability audit (Step 0)
The first 30 days aren’t about moving anything. They’re about knowing exactly where you stand before you do.
Knowing where your emails land can give you a competitive edge over those still relying solely on delivery rate metrics. Monitoring inbox placement helps you catch issues early and ensure your emails get seen by more people. – 2026 Validity Email Deliverability Benchmark Report
A deliverability audit covers:
- Domain reputation: where do inbox providers currently see your sending domain? Any red flags to address before you move?
- Authentication: are your SPF, DKIM, and DMARC records properly configured?
- Data hygiene: identify bounces, inactive subscribers, and high-risk contacts that could hurt your reputation if migrated without cleaning/suppressing.
- Daily deliverability testing: for 30 days, run seed tests to see where your emails actually land (inbox vs spam) across Gmail, Outlook, Yahoo.
Don’t skip this. Or you risk migrating a bad reputation onto a new platform without even knowing it.
Thatâs not going to help you sell tickets or land sponsorships.
Step 1: Full ESP inventory and data prep (Days 1â7)
While running the deliverability audit, inventory and clean up everything currently in your ESP:
- Emails: Campaigns, automations, templates.
- Tech integrations like Zapier, CRM, WordPress, etc.
- Subscriber fields and tags: audit, remove unused fields, merge duplicates, clean up tags, and create the final clean setup that is also ready for AI to read.
- Audience segmentation: identify your most and least engaged subscribers, identify groups based on purchase history, source, etc.
- Email validation: run your entire subscriber database through ZeroBounce or Mailercheck or similar.
Why this matters: You don’t want to move a messy system from one account to another. Declutter before the move and get ready to use AI in your email marketing in the process. (I wrote about what that should look like in my newsletter.)
Step 2: Set up the new ESP (Days 8â21)
- Configure DNS and authentication records (SPF, DKIM, DMARC)
- Set up account and brand details
- Recreate your email template
- Recreate automations
- Build forms, popups, landing pages
- Set up unsubscribe pages and preference pages
- Mirror your data set: updated fields, tags, and groups from the old platform
- Export unsubscribes and bounces from the old ESP and create a suppression list of ex-subscribers so no opted-out contacts get mailed.
- Test everything
This is not the time to create a new design and rethink your welcome flow. Recreate everything as is first, move, and once youâre settled, you can start thinking about making changes.
Suppression is essential. If you skip it and accidentally email someone who has unsubscribed, you’ve got a compliance problem and a spam complaint problem at the same time.
Step 3: Start the warm-up (Days 21â30)
- Test everything again
- Activate email confirmation sign-ups from the new platform
- Activate your lead magnet(s) to start sending from the new platform
- Activate new sign-up forms to route to the new ESP
- Start sending your regular newsletter to new subscribers from the new platform, and keep sending to your existing subscribers on the current platform
You are running two ESPs simultaneously at this point on purpose. Anyone mid-automation on the old platform should complete that journey there without interruption.
Creating a transition so smooth none of your subscribers notice is the goal.
đ Validity’s 2026 Benchmark Report puts global inbox placement at 87.2% in 2025. That means roughly 13% of legitimate marketing emails are still not reaching the inbox, even when nothing is going wrong.
“Mailbox providers are prioritizing user engagement as a primary trust signalâand brands that don’t adapt their strategies risk losing inbox visibility.â – Validity’s 2026 Benchmark Report
Test, test, and test again. I cannot reiterate how important this is. Most of the time when I start working with a new client, we find that some form somewhere on their site or social is sending old stuff out.
Step 4: Ramp up the warm-up (Day 30+)
- Export subscribers from the current ESP with all fields and tags, organised by engagement segments
- Import your most engaged subscribers first and add them to the regular newsletter on the new platform
- Monitor daily or weekly
- Gradually move less engaged subscribers across in groups (Day 45+)
Start with your most engaged. They’re the ones most likely to open, click, and signal to inbox providers that your new sending domain is legitimate. You want as many green signals from your subscribers as possible.
This is the foundation of your deliverability and keeping that healthy so you can be seen by your subscribers when needed.
Step 5: Ongoing checks (Day 30+)
Monitor your old ESP for new unsubscribes daily. Sync them into the new platform until unsubscribes stop coming through. Then you’re done.
Yes, youâre still paying for the old platform at this point, consider the duplicate cost in your budget.
What phase in your annual event cycle is best to migrate?
Is it your instinct to migrate just before you start selling your next eventâs tickets? Iâm afraid thatâs one of the worst timings for it.
During your sales phase, youâre ramping up your email volume and frequency, and youâll be sending attendee comms at the same time as well, so you need your emails to be seen.
You cannot risk landing in the spam folder or not landing in the inbox at all.
Hereâs when Iâd recommend getting started with your migration based on where you are in your annual event lifecycle:
| Annual event lifecycle phase | Deliverability steps | Whatâs happening to sending |
|---|---|---|
| Sales phase/Attendee comms | Do the deliverability audit, audit your ESP, start setting up your new ESP (Step 0-2) | All emails to go out from your current platform |
| The Event | Donât do anything, focus on your event | All emails to go out from your current platform |
| Follow-up | Start with step 3, keep current subscribers where they are but funnel new ones to the new platform | Emails to go out from a mix of your current and new platform |
| The Void (1-2 months)* | Once warmed up, start to gradually transition (Step 4) | Emails to go out from a mix of your current and new platform |
| The Void (3-5 months)* | Complete your transition (Step 4) and begin monitoring (Step 5) | Emails to go out from a mix of your current and new platform |
| The Void (6-9 months)* | Build that engagement, reputation and get as many positive signals from your subscribers as possible. | All emails to go out from your new platform |
*The timings above are simply examples. It may be a faster migration of steps 4 and 5 for you, or longer. Each plan needs to stay adaptable.
Yes, this means you need to pay for and manage two platforms at the same time, but itâs worth the benefits of a smooth transition and maintaining a positive reputation in the inbox.
The difference in doing all of this a year ahead, as per my above example, is that when the next sales cycle for your annual event comes around, you will have a warmed-up domain with a good reputation, ready for the sales push.
P.S. If you have a complex multi-event programme all year-round, you need to plan your migration very carefully. I would consider migrating an event or an audience group at a time over a long period so that youâre not raising red flags in the inbox.
If you do anything, do this
- Audit everything you have today and make sure that youâre not migrating one messy ESP into another, your problems will move with you.
- Develop a gradual, staged process that works with your timeline. It takes longer than you think. Donât do a cold cut download-upload move.
- Monitor your deliverability. Focus on getting as many positive engagement signals as possible.
- Keep things the same in the move, donât rebrand, redesign or restructure. Keep things simple.
Migrating ESPs takes 3â6 months, and you want to get it right from the beginning. If you’re starting that conversation now, book a discovery call, and we’ll map it to your event cycle.
“Maria worked with the Ickle Pickles Children’s Charity on transferring our email subscribers from MailChimp to MailerLite and set up several automated welcome sequences. She helped to transform our email marketing by mapping out email journeys, segmenting our subscribers into groups and targeting our supporters with appropriate email marketing.” – Kat Khalife, Marketing Manager at Ickle Pickles