The bloat stems from the use of numbered and bulleted lists in e-mail messages. Outgoing messages containing such lists will bulk up with "redundant CSS definitions." Consequently, mail services that limit the size of incoming messages may not display the messages correctly, according to Microsoft's Outlook 2010 blog.
Patches for both the 32-bit and 64-bit versions of the Outlook 2010 beta can be accessed here.
The fixes actually apply to Microsoft Word 2010 beta and are also available via the Microsoft Download Center as Knowledge Base article KB980028. Microsoft's Jeanne Sheldon explained in the Outlook 2010 blog that "though the problem is most readily manifested in Outlook, the root cause is in Word 2010."
Applying the patch will eliminate the bloat caused by future incoming messages, but it does not fix e-mails already received. Microsoft recommends running Outlook 2010's "conversation clean up" feature to reduce the mailbox size. The clean up feature removes older message threads while retaining the most current message in a thread, as described in this blog.
Microsoft fixed this bug in the release candidate version of Office 2010, according to a blog. However, the general public doesn't have easy access to the release candidate version as it was privately released to testers earlier this month.
The Office 2010 beta can run on the same hardware that was used to run Office 2007, according to Microsoft. Older versions of Office do not have to be removed before installing the beta, but Microsoft adds a couple of caveats. First, the Outlook 2010 beta does not play well with other versions of Outlook installed on the same machine. Second, SharePoint Workspace (formerly known as "Microsoft Office Groove 2007") does not coexist with earlier versions.
Microsoft recommends selecting the "custom installation" option of the Office 2010 beta installation program if users want to exclude Outlook 2010 and SharePoint Workspace to avoid conflicts with older versions of those programs. Otherwise, the "express installation" option will add those applications.
Important details to know before installing the Office 2010 beta are described in this blog.
Office 2010 is expected to become generally available in June. Betas for a number of Microsoft's 2010-branded products were released in November.