Cloudiway uses the autodiscovery process to determine Office 365 servers.
This article explains how it works.

If you’re not familiar with the autodiscover feature of the exchange servers, please read the following articles:
AutoDiscover configuration for Exchange 2007 and 2010
Exchange Autodiscover

By default, Cloudiway migration uses the autodiscovery process to locate Exchange servers (or online Exchange servers).

For Office 365, if the autodiscovery mechanism doesn’t work, Cloudiway automatically falls back to outlook.office365.com.
For Exchange servers, if the autodiscovery mechanism doesn’t work, you can manually set the server name:
Exchange Connector

Note for Office 365:
The licence must not be a kiosk licence (see http://support.microsoft.com/kb/2826047/en-us)