We have been having an ongoing issue with our marketing emails loading slowly in iPhone’s native Mail app. Emails open with a couple of seconds in other mail apps (gmail, etc), and on desktop but can take upwards of 45 seconds to load in the iPhone mail app, and people just aren’t going to wait that long. Image-heavy marketing emails from other companies open quickly in the iPhone app, so the issue seems to be our emails. We were using a coded template for emails and recently switched to a drag-and-drop template hoping that would alleviate the issue. It did not.
We have noticed anecdotally that load time is faster if we’re using cell data rather than Wi-Fi.
Has anyone else experienced this issue, and if so, were you able to find a solution? We’re stumped.
Hi @MaryMoon! Welcome to the Community-- happy to have you here 
I understand your marketing emails are loading slowly on iPhone mail app. I appreciate you trying out some troubleshooting. Have you attempted this on multiple iPhones and multiple Wi-Fi networks?
I recommend also reviewing how to Preview and optimize how your email appears across clients and devices in the HubSpot Knowledge Base. For example, it suggests:
In most cases, download speeds on mobile devices are slower than on desktop. Use smaller image files to decrease your email load time. HubSpot automatically resizes your images that include a width attribute in an <img> tag. Services such as FastStone Photo Resizer and JPEGmini can also reduce file size by as much as 80% without reducing the quality of your image.
Best,
Kennedy
Thank you for the resources. Yes, we are seeing this across multiple iPhone devices and Wi-Fi networks.
Thanks for confirming @MaryMoon. Likely if you are not seeing this slow loading time on any other apps or a desktop, then it may be an isolated issue to the Apple Mail app itself. Have you attempted to download Outlook or Gmail on iPhone and load the email directly from the email provider app?
It is limited to the Apple Mail app. The emails are opening without issue in the Gmail app on iPhone and in Outlook on iPhone. At this point, we’re not really sure what steps to take to resolve the issue. We are not using any custom coding in our email templates - everything is fully drag-and-drop, and we are compressing images.
Another confusing thing we are noticing is that when you click on one of our emails in the mail app, the email attempts to load (with spinning ‘loading’ circle showing), but if you back out of the email and then click back into it, it loads immediately. We know our audience won’t do this, but it is an odd thing that we are seeing.