http://bugs.winehq.org/show_bug.cgi?id=25870
--- Comment #1 from David turbolad995@hotmail.co.uk 2011-02-05 19:11:44 CST --- This is best tried with Pegasus Mail: www.pmail.com
Download and install. When installed, you will see some 'introduction' e-mails (which tell you a little bit about Pegasus Mail). The column headers do nothing when you double left-click the vertical dividers; they are supposed to resize the entire column to fit the text contents below, optimally.
Having Googled this, I come across this msdn page, not sure if it's the right one (?), but it does say: "Users can also double-click a divider to automatically resize the associated row, column, or header band based on its contents." http://msdn.microsoft.com/en-us/library/ms171604.aspx
Hope that helps? :)