Your username is the actual name of the mailbox on the Exchange server. This name was set by your account administrator when your mailbox was created. It could be in the format of firstname.lastname, or firstname, and is unique to your mailbox. For example, if your name is John Doe, your username could be john or john.doe.
Your primary email address (in EcoCloud360 environment, this is also your User Principal Name, or UPN) is associated with your mailbox username. It will also appear in the From field of the messages others receive from your mailbox. You will be able to receive messages using other email addresses, but not send messages from them.
In order to log in to your Exchange mailbox, you need to either use your Exchange domain and username, or your primary email address.
You can find your primary email address in Home » Service Director » Exchange Hosting » Exchange Accounts » Manage Service. Click the display name of the user under Display Name column. On the General settings tab, the address is shown in User.