Not from the platform but you could do a group/bulk PM. We use a separate tool for email comms as the LI platform doesn't have an email comms tool for that type of use.
You our could export all user emails and use a mailer app to mass mail them?
You don't @niiiiiiiiiik.
Hence the need for something like this http://community.lithium.com/t5/Product-Ideas/Build-a-Message-Manager/idi-p/186374 that you could use to email everyone except those that have opted out.