Email slow when downloading from iCloud

I have this problem, too. [MacBook Pro M1, Big Sur 11.4] Each and every individual mail piece from iCloud can take a full minute to download. It sped up over the weekend, but is back to slowpoke today. The other mail that I have delivered to my Mac Apple Mail via Verizon, Yahoo, and GMail addresses are lightening fast. It is just the @iCloud.com mail that is so slow. Also, the mail is delivered to my iPhone and Apple Watch up to a half hour before it tries to arrive on my MacBook Pro M1.

I have the same problem. I’ve had my Mac account for probably 20 years and never had this problem before. It’s happening on both my iPad and iPhone, whether using home WiFi or 4g, whether at home or away from home. I’m working from home nowadays and I have no problem getting instant downloads of emails on my Microsoft accounts or Microsoft teams videos. It’s not me, or my internet connection. It’s the mac email account. What do I do …??! It’s become unusable.

It's not getting any better. I find myself deleting some emails before they fully load because I anticipate what they'll say. Not a good practice. Frustration is high. When is Apple going to fix this?

I filed a bug report ("feedback") via their feedback assistant (FB9201629). They asked for a piece of information to help investigate, but didn't give any kind of instructions about where to find that information. :-( I sent it back, asking where to find the information they want. I think I may have found it by poking around in Keychain Access, but we'll have to see if they follow through.

This evening, on all of my devices (iPhone, iPad, iMac), my inbox showed no messages for a while (eek!), then began downloading all (thousands!) of my messages. So far, it is significantly faster than it has been previously, though it's got a lot more to download.

I'm guessing that something in the server's configuration changed (including resetting of message numbers). Here's hoping that includes a fix for the intermittent performance problems we've been seeing.

I have this same problem. Doesn't seem like there's any solution to it yet. Any chance you're seeing something like this? https://vimeo.com/536162467

This is the most detailed description of the problem I’ve seen yet. Thanks for sharing. Hopefully Apple will acknowledge this soon.

I totally agree, I had an email this afternoon that took 30 minutes to load. it is ridiculous.