The goal of this document is to detail the advantages of using Cloud MailStore Server instead of Office 365 archiving for email archiving based on provable facts as opposed to mere assumptions or hearsay. To achieve this goal, only statements about Office 365 archiving that are based on publicly available material published by Microsoft are taken into account. These statements are compared to the capabilities of Cloud MailStore Server, based on equally publicly available material published by Cloud MailStore Software. To further enhance the quality of this analysis, all statements (with the exception of those related to pricing) have been extracted from technical specifications and implementation guides to ensure that they are based on current best practice and state of affairs.This document supersedes all previous versions and has been updated to the latest information available in April 2014.