E-mail may not seem the hottest of areas, but two developments this week show there may yet be some room for innovation in the messaging market.

Yahoo acquired open-source collaboration/e-mail vendor Zimbra for $350 million. Meanwhile, the Mozilla Foundation—best known for developing the Firefox browser—is funding new development targeted specifically at open-source email solutions.

Large-scale, open-source-based email solutions from Zimbra/Yahoo and Mozilla will likely appeal to service provider and ISP customers in particular as they look to take their own branded email and messaging services to the next level.

Yahoo’s acquisition of Zimbra is getting a lot of attention for the “Web office” angle—among its offerings, Zimbra makes an online alternative to Microsoft Office apps like Word and Excel. Zimbra’s email server and client technology has been released as open source, though the vendor sells commercial, supported versions as well to large university, service provider and enterprise customers.

While large-scale email systems—especially in the enterprise—remain largely the province of Microsoft Exchange/Outlook (with IBM/Lotus holding strong as well), Zimbra made inroads with its open-source model and innovative approaches to email and collaboration on both the client and server. In addition to a slick AJAX client, Zimbra has developed over-the-air push synchronization capabilities for mobile devices akin to BlackBerry email service.

In an interesting coincidence, the Mozilla Foundation announced an initiative to focus more energy and resources on Internet email and communications, building new products based on its Thunderbird product, code and brand. In particular, Mozilla hopes to foster a development community working in the areas of email and communications the same way that developers have focused on building extensions and add-ons for its Firefox browser.

Mozilla will initially provide $3 million dollars in seed funding to launch MailCo, a small team that will spearhead work in this area. It will be led by new hire David Ascher, currently Chief Technology Officer and vice president of engineering for open-source tools vendor ActiveState.

Mailco is quiet for now on future directions, but potential avenues to be pursued include further integration of other communications-centric applications into the email client, including instant messaging, SMS, RSS, social networking and more. Also possible is a focus on a more seamless approach to online email (Webmail) and offline email (a client-based approach).