Yahoo Zimbra Desktop offers Yahoo Mail users offline access to their Webmail accounts, as well as providing document and spreadsheet support. As with Yahoo's Webmail interface, it mirrors Microsoft Outlook's look and keyboard shortcuts.
Zimbra Desktop can handle multiple accounts, including access to the competition. Configuring for Gmail, or any other mail service, was dead simple. One similarity to Gmail are the small triangles that appear next to e-mail messages that are part of a back-and-forth exchange. Clicking on the triangle expands the e-mail header list so you can see all the messages of the exchange. There's also tagging, which Zimbra uses much like Gmail's labels. Unfortunately, Zimbra's tags and Gmail's labels didn't synchronize. And tags are specific to an e-mail account, so clicking on a tag will show only a subset of messages within one.
However, it's not perfect. It didn't seem connected to our Yahoo address book for contacts or calendar for events. And unless you instruct it otherwise, Zimbra Desktop will synchronize your in-box but not folders where you may have filed message. You can manually sync folders when you click on them, but the process worked erratically.
Zimbra Desktop's productivity suite elements are workable, but barely so. Unlike Google Docs, Microsoft Office files can't be opened, and there's no presentation software. The spreadsheet is extremely spartan, and runs awkwardly inside the word-processing application. Stability also became an issue when running a spreadsheet and minimized applications.