Exchange Online and Exchange Server: Choosing and Integrating

Exchange Online offers a key advantage over Exchange Server: larger, more scalable e-mail systems with less investment in data center infrastructure and expertise.  

On features, Exchange Online was once slightly behind the Exchange Server software, but it has advanced technically beyond Exchange Server in calendars, tasks, compliance, security, and other areas:

Calendar management is integrated with Teams , and with appointment scheduling with external users. 

Task management with To Do offers more options for organizing tasks, and is being tied together with Planner to coordinate a user’s own agenda with projects the user participates in.

Retention and eDiscovery for Teams messages, and integration with Microsoft Purview services for more capable retention and data loss prevention than the functions built into Exchange Server and Active Directory. 

Message security for spam, domain forgery, phishing, and novel types of malware benefits from Microsoft’s enormous operations centers and its ability to collect data from hundreds of millions of users. However, many of the messaging security services that Exchange Online uses are also available for Exchange Server.