As you know the EWS Java API, a java client library to access Exchange Web Services (EWS) - a SOAP-based API and you can use it from Java or any other language that lets you POST XML data over HTTP. The API works against Office 365 Exchange Online as well as on premises Exchange Server.

Recent update is that it’s available on GitHub as an open source project, ews-java-api and here is the official announcement for it.  If you’re interested to use EWS API in your project, then you can get it started by looking at the following documentation and Mike’s post on this. Smile