It's odd to see iCloud's mail servers have so many issues within a few days of each other. Again, this morning at 8:05, my @me.com email account failed to check for new mail. The iCloud.com mail access is also unavailable. The only action I can perform at this time is sending email, which accesses the SMTP servers, suggesting that they're still working fine. The case was the same a few days back.
Apple has yet to acknowledge iCloud mail's disappearance.
Update 11 AM: All is well.