Starting with one of the most important factors security, which has been the big concern for many companies considering moving to the cloud. Microsoft’s online services have been designed with security in mind. Office 365 applications are accessed through 128-bit SSL/TSL encryption so that if a transmission is intercepted by someone without authorization, they won’t be able to read it. Antivirus signatures are kept up to date, and security measures are applied in accordance with the Microsoft Trustworthy Computing initiative. Exchange Online uses Forefront Online Protection for Exchange (FOPE) to protect mail messages from malware, and it uses anti-spam filtering and antivirus with multiple virus engines. You can read more about the security of Microsoft Online Services here.