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Will iOS 15 break the internet?

3 Minute Read

Tennis net with one broken piece

Daniel SmithSr. Platform Architect, Cordial

This is a continuation of our series on iOS 15’s Mail Privacy Protection (MPP) and our deep dive to answer some questions from our previous post – check it out here. Today’s update contains minimal analysis as we believe the data speaks for itself. The most surprising update on networks is that Apple seems to have stopped most traffic through Fastly.  

We’re more than two weeks past the public launch of iOS 15 and the growth continues to be steady. The first of our parting questions asked whether we would start to see an impact on the overall open rate observed by Cordial. We have:

Raw Opens by Source Network

MPP definitely affects our global open rate and no one is surprised about that, though the additional 7 days of data allowed us to see the trend more clearly. Interestingly, the share of open data generated by the three CDNs (Akamai, Cloudflare, and Fastly) has remained relatively flat:

iOS as a share of total

We continue to hunt for other involved CDNs but haven’t been able to find any that have a significant share of traffic to be noticed. 

This problem is akin to understanding whether someone’s email address is actually served by Gmail. For this data, our network identification process continues to be manual and we’ve only established ownership for the top 85 networks by request volume. 

In our previous post, we asked whether other traffic from Cloudflare might obscure the reality of traffic from iOS 15. After much checking and re-checking, only 35 opens per day appear to come via Cloudflare’s WARP product.

This leaves us with a single burning question: Will iOS 15 break the internet? 

While not an entirely serious question, there is some concern about the bandwidth required to deliver not just open pixels, but every image in every message sent to iOS 15 with MPP enabled. Cordial serves the vast majority of images for every email delivered through our platform and our initial guess was that our bandwidth utilization would triple as a result of this rollout. This view of image traffic broken out by source network is both expected and mildly alarming:

CDNs verses others

This is the first time we’ve broken out bandwidth by CDN (all shades of blue, notice Fastly is almost non-existent now) and non-CDN traffic. Our expectation is that iOS’ share of traffic on our network will approach 55% – almost double the share of traffic in iOS’ second week of availability. October 2 and October 4 were Cordial’s highest days for image content serving in history. Our recommendation is that any company hosting their own email images look for an alternative option that is low cost, or even free.

As we continue tracking early adoption, stay tuned for our next article in our iOS 15 series, which will look at the unanswered questions and drill deeper into new data as it emerges. 

For further reading on this topic, check out these resources: