While some of the team have been putting the finishing touches on our new A/B split testing feature, we’ve also been hard at work on a range of speed improvements we plan on making across Campaign Monitor.

We’ve been consistently growing at more than 1,000 new customers each week for the last year now. While this is nothing short of awesome, it also means we need to be conscious of our own infrastructure. Today we completed a significant database upgrade that brings with it a host of speed improvements across the application as well as much improved scalability.

Serving your images from 15 key locations

On top of this upgrade, we also pushed a big improvement to how we render images in your recipients email clients. Traditionally, all images in HTML emails were served from our main data center in North Carolina. As of today, all campaign images are now served from a global Content Delivery Network (CDN) across North America, Europe, Asia and Australia. Here’s a quick map to show you the locations your campaigns are now being served from.


Whenever you import a HTML email campaign or template, we’ll automatically cache copies of that content across 15 key locations around the world. Whenever a recipient opens your campaign, we’ll choose the optimal data centre and serve your image content directly from there. This results in a dramatic reduction in email load times for many of your recipients. The best part is, it’s completely automated, free of charge and available now.

For those customers using custom domains, your images will also be served from the CDN by default (which uses the createsend domain). All tracking links will still use your custom domain, and you can have the CDN switched off in your account at any stage by getting in touch with our support team and requesting it.

A better experience for your subscribers

This update ensures image-based campaign content will now render significantly faster for all subscribers. A reduction in load times reducing the chances of a recipient getting impatient and moving on to the next email in their inbox.

Added redundancy

As well as a big speed increase in rendering times, this update also provides additional redundancy for your campaigns. If one data center is unavailable, the content will be served from the next closest location. Think of it like 15 backups of your campaign in highly secure, reliable locations around the world, not to mention the addition backup procedures we have place in our main data center.

Lots more to come

Now that your email campaigns are rendered faster, we’re moving on to more speed increases to the software itself. The first step will be serving all Campaign Monitor assets (images, CSS files, scripts, etc) from the CDN too. We’re also switching to a much slimmer JavaScript library and optimizing the majority of files to keep the footprint of the software to a minimum.

While this is happening, we’re also warming up a second data center location that we’ll be load balancing between. This will give us another nice speed boost, add an extra level of redundancy to every layer of our platform and give us an additional range of IP’s to deliver campaigns from. We’ll be sharing more details about the benefits of this soon, but I wanted to keep you all in the loop about some of the exciting behind the scenes improvements coming to Campaign Monitor over the coming months.

  • Paul Stone

    That’s great news about the CDN for images. One question though: if we make changes to one of our images, should we rename it/use filename versioning (like https://www.campaignmonitor.com/assets/uploads/image-v1.jpg, https://www.campaignmonitor.com/assets/uploads/image-v2.jpg) rather than upload it with the same name. I know that some CDNs won’t repopulate the cache if you simply upload a filename with the same name…


  • David Greiner

    Hey Paul, glad you dig the update. You’ll be pleased to know we automatically update the cache across the CDN if any images are replaced when a campaign is re-imported. We’ve got your back on that one.

  • Y McGauley

    Great stuff CM, a very nice addition to your excellent services already.

  • Alex Duffield

    Absolutely Brilliant. Thanks for taking an proactive approach.

  • Sebus

    Cool, and thanks a lot !

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