Context: I had two accounts configured in my Mail.app - an Exchange account for work, and a personal iCloud account. I've had the iCloud account since it was .me, and it has worked fine until recently. It also continues to work fine on my iPad and iPhone and on the iCloud website. So here is what I have experienced...
In August, this account stopped working on my mid-2010 MacBook Pro. I started getting errors telling me my password was not accepted by the account anymore, and no matter what I tried, I could never get the account working on that MacBook after that. I didn't really care that much at the time because I knew I was getting a new one soon, and sure enough I did. I received my MacBook Pro with Retina sometime in September.
On day one, I configured all of my account settings through iCloud and the Mail app, and everything was great. Emails coming in and going out, notes being perfectly synced... it was great. This lasted until Thursday or Friday of last week. I powered up my MacBook and saw my iCloud account was offline in Mail. When I tried to take it online, I received (and still receive when I try to set it up) this error:
"The iCloud IMAP server “p01-imap.mail.me.com” is not responding. Try checking the network connection, and that the server name is correct. Otherwise, the server might be temporarily unavailable. If you continue, you might not be able to receive messages."
I know the credentials are accurate, I know my Internet is fine (and I've done this at multiple locations, home/work/Beaners), and I know I've tried every troubleshooting step I can find for this. I did the signing out of iCloud and rebooting thing, that did not work. I also cannot enable mail or notes through the iCloud preference pane. I know this because when I try, I receive the following error:
"iCloud Mail couldn't be enabled from the iCloud Preference Pane."
It then suggests for me to set it up through the Mail app.
Here we are.