Security is the primary reason businesses are hesitant to switch to the cloud-based Microsoft Office 365. But adoption continues to grow despite fears of spearphishing and ransomware attacks. Exchange Online is the most commonly used tool in Office 365, followed by OneDrive for Business (70.9%) and SharePoint Online (56.8%) Only 15.6% of respondents use Office 365 Advanced Threat Protection (ATP) Only 8.5% have set up Domain-based Message Authentication, Reporting & Conformance protocols.”]
Source: https://www.darkreading.com/cloud/security-no-1-inhibitor-to-microsoft-office-365-adoption