Browse by...
Home Resources Blog

One big part of the merger between Campaign Monitor and MailBuild was the need to maintain backwards compatibility. Both apps had their subtle differences, and we’ve worked hard to make sure everything like subscribe forms, campaign archives and client login forms continue to work just like they used to.

The same goes for the API. All current implementations of the API will continue to work, but there are some important changes Campaign Monitor customers need to know about for any future API work. MailBuild customers can relax, you don’t need to make any changes and instead get access to lots of new functionality.

Campaign Monitor API users should keep in mind that these changes only apply to those wanting to start new API development, or update any current implementations. All current API code will continue to work nicely. Here are the key differences you should be aware of.

New API keys

If you have previously generated an API key, you’ll need to generate a new key for any future API work. To get the key, head into “Account Settings”, and you’ll see the key at the bottom of the page.


All IDs are now encoded

All IDs for your lists, clients and campaigns are now hexadecimal strings instead of the old integer format. This is how it worked in MailBuild all along, and will be the standard moving forward. If you switch to the new API key, you’ll need to make sure you grab the new encoded IDs from your account too.

You can grab your client ID under Client Settings, and your list IDs by clicking the “Edit list name/type” link on each subscriber list’s page.

New API endpoint

For all future use, the API endpoint will be

The important thing to remember here is that you can’t mix and match between the old API key and new endpoints and ID’s. Right now we’re working on updating all the API kits to use the new API approach, and they’ll be trickling out over the next couple of weeks. The same applies for all the cool plugins that have been built for the API over the years for Drupal, ExpressionEngine, Mint and loads more.

This blog provides general information and discussion about email marketing and related subjects. The content provided in this blog ("Content”), should not be construed as and is not intended to constitute financial, legal or tax advice. You should seek the advice of professionals prior to acting upon any information contained in the Content. All Content is provided strictly “as is” and we make no warranty or representation of any kind regarding the Content.
Straight to your inbox

Get the best email and digital marketing content delivered.

Join 250,000 in-the-know marketers and get the latest marketing tips, tactics, and news right in your inbox.


Get started with Campaign Monitor today.

With our powerful yet easy-to-use tools, it's never been easier to make an impact with email marketing.

Try it for free