The e-mail server was upgraded tonight to the latest version of Zimbra — version 6.1. Even though this upgrade is considered a “major” revision (from 5.x to 6.x), the resulting change to you, the user, should be fairly minimal. The web interface is mostly the same, with some minor UI improvements and changes. Hopefully nothing is too confusing.
The most annoying thing I’ve found thus far is the inability to change from the “advanced” version of the web client to the “simple” (and vice versa) while in mid-flight. There used to be a link to swap back and forth on the main page, but that link is no longer there. So if you prefer the “simple” client, be sure to choose it when you first log in.
Also, in case you were wondering, this would have been why you wouldn’t have been able to access your email sporadically between 6PM and about 10:30PM PDT today.