I wanted to move an Exchange account with e-mail and calendar to Office365. This turned out to be a bit more tricky than I thought. First of all, I thought I could migrate the data from one server to the other by simply opening both the old and new accounts in Outlook. This way turned out to be a dead end, because it's not possible to configure two accounts with the same e-mail address. And in addition, it's impossible to change the name of an existing account. In order to migrate the e-mail and calendar data, I used the export function to get a large Outlook file with all the data. The next hurdle is to get rid of the old account in the settings. Outlook refuses to delete the "last" account. One way to go is to delete the Outlook profile. When re-starting Outlook, it's as if it's set up anew and accepts the newly created Office365 account. The old data can be imported via file. If there's much data the upload can take a while.