We’ve heard your concerns and take them seriously. We’re looking into what we can do to improve this situation for you, nothing definitive yet but be assured we’re working on it and will post an update asap.
Update 11/30/2012: Please note, ExBPA content does not have multiple versions. Content (links from the ExBPA tool) may currently display "Exchange 2013" as the version, but it's the same content the ExBPA tool linked to earlier. The CMS team is working to fix this.
Quick note to inform you that we've updated Exchange TechNet Library. Starting today, if you've bookmarked an Exchange 2010 article in the library (for example, http://technet.microsoft.com/en-us/library/bb124558.aspx), it'll take you to the Exchange 2013 version of the article.
Note, if an Exchange 2013 version of the article does not exist, the URL will still take you to the Exchange 2010 version.
How do I get to documentation for previous versions?
Other versions menu You can still reach the Exchange 2010 version of a particular article by using the Other versions option right below the page title.
Append version info You can also get to the Exchange 2010 version of a particular article by appending version information (EXCHG.141) for Exchange 2010) at the end of the URL, right before the file extension (.aspx). So the Exchange 2010 version of the above URL will be http://technet.microsoft.com/en-us/library/bb124558(EXCHG.141).aspx. Please update your browser favorites/shortcuts and links in any blog posts if you still want them to point to the Exchange 2010 versions.
Navigation tree You can use the navigation tree (on the left side of each page) to easily navigate to documentation for each Exchange Server version.
Short URLs You can also get to the main documentation page for each Exchange Server version by using the following short URLs:
Download help files You can also download the standalone help files in compiled HTML format (aka CHMs) from the following locations:
11/12/2013: Post updated to show additional navigation options and links to help file downloads.