File this one under the “nice to know but not much to be done about it” category. Over the past week, we and many other iCloud and Gmail users have started to notice that some, but not all, messages from Gmail to iCloud have been delayed, sometimes for days, or even rejected after too much time has passed. A number of threads at Apple Support Communities (such as this one) have talked through all the variables, and it simply seems that there’s something deep within the guts of iCloud that is having trouble receiving mail from Gmail. Some people have commented that email delivery from other services seems to be affected as well, but we haven’t yet been able to track down
any patterns there.
As I noted, there doesn’t seem to be any way to work around this problem. Neither Gmail nor iCloud offer users any insight into or much control over their inner workings, so we’ll just have to wait and let Apple’s and Google’s email administrators figure out and solve the problem.
In the meantime, if you have a non-iCloud email address, it would be worth telling your Gmail-based correspondents to use it instead. And if you forward your Gmail account to iCloud, consider logging in to Gmail directly to check mail there until this is resolved.