Now this is interesting, even if you're not a Yahoo! Mail user. Yahoo! has released the Beta 3 version of its Zimbra Desktop, which is essentially Yahoo! Mail (or, amazingly, Gmail or AOL, or any other IMAP/POP mail) running as a local application (with Windows, Mac, and Linux versions), using Mozilla Prism technology. (You can use Prism to make standalone versions of Google Calendar and Gmail, though they're still online-only Web apps at this time.) The Zimbra blog has some details:

We’ve aimed to blur the line between a Ajax web-client and a conventional desktop application, and this release is a leap towards reaching that goal. If you’re just joining us here’s the best part: It’s an offline capable client so you can take your data with you whenever you don’t have internet access - then sync any type of interaction that you can do in normal webmail access when you get connected again. So many cool new things I don’t know where to begin - the Zimbra Desktop team has been very busy since Beta 2.

Your tasks, documents, & briefcase items can now follow you wherever you may roam. If you’re already using Zimbra Desktop against a Zimbra Collaboration Suite server these will show up on next edit or item move via delta sync - while a full account sync or reset will pull in prior items. Personally, having briefcase items available offline is a major plus - as offline calendaring using the same AJAX web-client interface has already long since won me over.

Yahoo! Mail users rejoice - There’s now IMAP access through Zimbra Desktop to all free, plus, and business accounts. You didn’t read that wrong. Normally only Plus accounts have POP access, but as a perk when using Zimbra Desktop the mail is synced via IMAP; which is a much better protocol for keeping your mail organized - and yes it’s available to free accounts as well. Hook-up your @yahoo.com account or go grab one of the new @ymail.com and @rocketmail.com addresses. (Note that some apps don’t sync to Yahoo! servers yet so the data is local.)

Mailto: link handler - For Mac and Windows protocol handlers allow you to click on a mailto: link in any browser, and it will bring-up Zimbra Desktop’s composer with a javascript call. If Prism is not already running, it will start the web-app as well with a url call, then pop up compose. We don’t want to be accidentally invasive, so to turn this feature on you’ll have to check the box in global preferences to make it the default mail client on your computer.

There’s also easy setup menus for setting up Zimbra Server, Yahoo! Mail, GMail, AOL, or any other IMAP/POP accounts you want to use. For Beta 3 we’ve thrown out JavaMail and wrote a brand-new robust IMAP/POP client-engine from scratch.

There's a lot more but this looks really sweet. Google and Microsoft (and Apple, I guess) need to get their act together: This looks like the new standard for cloud computing email solutions.

And for the record, how weird is it to access Gmail over IMAP via the new Yahoo! Mail interface? Very weird. But very cool.

Related: Yahoo! Zimbra Desktop