n-Campaign Monitor's API Is Genuinely Open. Most Businesses Never Touch It Directly.
Campaign Monitor runs a documented REST API, built on what used to be called the createsend API, covering subscriber lists, campaigns, templates, and transactional sending, organized around a Client ID and a List ID that identify your account and each specific list. It's a real, usable API, which is exactly why Zapier, Google Sheets, and HubSpot all have ways to talk to Campaign Monitor through it. Wiring up anything beyond the common no-code cases still takes real development work, and that's what we build.
What the Campaign Monitor API actually covers
The API handles the core operations you'd expect: creating and managing subscriber lists, adding or removing contacts, sending campaigns, pulling reporting data, and sending transactional email outside your regular marketing sends. Every call is scoped to a Client ID, your account, and usually a List ID, a specific subscriber list, which is the main thing that trips people up the first time they read the docs. Find those two identifiers first and most of the rest follows a predictable pattern.
Webhooks are available too, so an integration can react when someone subscribes, unsubscribes, or a campaign event fires, instead of polling the API on a schedule and hoping nothing slipped through between checks.
No-code options exist on top of the raw API: a Zapier integration covers common triggers and actions without writing code, and connectors for tools like Google Sheets and HubSpot handle basic list and campaign sync. They're genuinely useful for simple, standard cases, and genuinely limited the moment the workflow needs conditional logic, custom field mapping, or a trigger those tools don't expose.
Why businesses end up hiring this out
Reading the API docs and making one test call is a short afternoon. Keeping a List ID and Client ID straight across dozens of lists, handling webhook retries correctly, and making sure a failed sync doesn't quietly drop a contact is a different scope of work entirely, which is exactly why the no-code connectors exist in the first place and exactly why they still fall short for anything non-standard.
The honest question usually isn't whether the API supports what you need; it usually does, within the bounds above. It's whether building and maintaining that integration correctly is worth your own developer's time against having someone who's already done it build it once.
What We Build Against Campaign Monitor's API
Custom sync beyond Zapier's default triggers
When a workflow needs conditional logic, a custom field, or a trigger Zapier and the standard connectors don't expose, we build it directly against the Campaign Monitor API instead.
Webhook-driven updates instead of scheduled polling
We wire Campaign Monitor's webhooks into the rest of your stack so a subscribe, unsubscribe, or campaign event updates your other systems immediately, not on the next scheduled check.
Not sure if the Campaign Monitor API covers what you're trying to do?
Describe the data you need in or out of Campaign Monitor, and we'll give you a straight answer on whether the API supports it or whether it needs a different approach.
Outgrown what Zapier or a basic connector can do with Campaign Monitor?
Tell us what you're trying to move between Campaign Monitor and the rest of your systems, and we'll scope it honestly against the real API. Campaign Monitor happens to have one of the more straightforward APIs we work with; the same build-it-properly approach applies to whatever else in your stack still runs on a workaround.
Let's talk