The outage began at 5:06 a.m. Pacific Time, and affected users may not be able to access their mail until the issue is resolved, which is the same problem that the service was having yesterday.
Apple has not provided a timeline on when a fix might be available, but we'll update this article when the outage has been addressed. Yesterday's outage lasted for several hours, and has recurred twice now.
Update: Apple says that the outage has been resolved.
