Performance Marketing

Considering Switching ESPs? Here is What You Need to Know

BY: Robin Glanz

PUBLISHED: 5/9/2016

The decision to switch ESPs isn’t easy. There are many considerations to be taken into account, including delay in sending, the level of effort, and ROI.


But once you make the decision, how do you ensure a seamless transition?


Before embarking on an ESP migration, we recommend gathering the following information from your existing ESP:

  • Outline the infrastructure/hierarchy you’re familiar with. You will want to replicate that structure or improve upon it for efficiency in the new platform.
  • Identify and define the lists, groups, segments or cells you have in the existing platform.
  • Take the time to clean-up any overlapping, disparate or out-of-date segments.
  • Make sure you identify and transition your unsubscribes and bounced email addresses.
  • Ask for the process for maintaining the unsubscribe link URL in historical campaigns and ensure you will be receiving any latent unsubscribes from your current ESP for transfer into your new ESP for 45 days after the migration.
  • Identify any specific segments or domains that may have been causing deliverability issues.
  • Document the attributes that you will want to extract and include in your new ESP.
  • Outline the infrastructure/hierarchy of your asset library.
  • Back-up or export any images and assets that you will need on the new ESP.
  • Understand how long your existing ESP will continue to hold the images in your account. Past emails won’t render images once they are removed from the image source.
  • Document the business rules for your triggered campaigns and marketing automations for replication in the new platform.


It's good practice to consult with your migration partner or new platform team to ensure that everyone is on the same page. This is a sometimes overlooked, but vital component to a successful migration.


Once you have a clear understanding of what you have in the current platform and what you want to migrate, put together a project plan with timelines and milestones to ensure the project stays on track. You want to prevent as much potential downtime as possible.

What should be included in your ESP migration? Here's the short list:

Migrate all subscribers.


Include as much detail as possible, including but not limited to, attributes, the number of emails delivered, the number of emails opened, the number of emails clicked, the last date of engagement (open and click), unsubscribe details, etc.
Include attributes for each subscriber, for example, first name, last name, birthdate.


Migrate all templates and assets.


Map out your IP warming strategy.


ISPs will require a ramp-up period from the new platform. Understanding the domain volumes within your audience will determine how long the warming period will last.


Continue sending from your existing platform for the duration of the IP warming period. While this involves two platforms and commitments, it provides the best stability for your email program through the migration.


Having a clear understanding of what you are doing before you have to do it will help maintain a low risk of error. Thus, leading to a less stressful transition between the two platforms.


For assistance with an upcoming ESP migration, reach out to MERGE.