With the Workbooks Exchange Server Sync you can select the emails that you would like to synchronise with Workbooks, in Outlook, by categorising them as 'Workbooks'. Despite the 'in Outlook' statement, this is true for any email client that is configured to work with Exchange server.
Any client that supports email categorizing feature (Windows Outlook, Outlook for Mac, Exchange Web Application, mobile clients etc.) can share an email in this way. Gmail does have a categorising feature so this will in turn be available, however it is not immediately obvious how to categorise in Gmail. For more information on how to carry this out please click here.