iCloud Mail has problems again less than a week away from 12-hour unavailability of all Apple services, but in this case we are not talking about the impossibility of using the service completely. More precisely, in this case it seems that the iCloud Mail servers refuse to send or receive in particular cases of emails to/from Gmail, sometimes they reach users with a delay, sometimes they display the error: 451 4.5.3 Too many rejections; try again later. .
Whether you have an email address @ icloud.com or @ me.com, the problem can affect you regardless of the situation, but if you haven't encountered it yet, then it's very likely that you won't. Given that we are talking about a problem that affects a very large number of users, Apple's engineers have been working for several days to solve the problems, but for now no one knows when everything will return to normal.
They are very aware of the issue and working on fixing it. They said that everyone who is having this issue should call and report this. They'll ask you for some info that will help them. They [sic] tech said specifically that the more people that call, the easier it will be to get a fix.
Although we are talking about a recent problem of the interconnection between iCloud and Gmail, I have to admit that I have repeatedly noticed that the iCloud servers have difficulty sending emails to Gmail or even Yahoo!. Unfortunately, those from Apple failed to create a very efficient system for sending emails, the delay in many cases being even a few minutes, it being still smaller than in the case of sending emails between Yahoo! and Gmail.
