1. Determine the mailbox server name and the proxy server URL. To do this, follow these steps:
a. Sign in to the Office 365 portal.
b. Click Outlook to open Microsoft Outlook Web App.
c. In the upper-right corner of the page, click the Help icon (the question mark), and then click About.
Locate Host name and note its address.
As an example in the case below the Host name is amsprd0406.outlook.com and yours will be something similar:
This value will be used later as proxy server for Exchange URL
As an example if your Host name value is amsprd0406.outlook.com , you need to change it to amsprd0406.mailbox.outlook.com
This value later will be use as Mailbox server name when configuring your Outlook profile.
2. Manually configure Outlook to connect to Exchange Online.
To do this, follow these steps:
a. Click Start, click Control Panel, and then click Mail.
d. Click to select the Manually configure server settings or additional server types check box, and then click Next.
e. Select Microsoft Exchange or compatible service, and then click Next.
f. In the Server box, type the mailbox server name that you noted in step 1d. In this example:
h. In the User Name box, type your user name (for example in this case, amin.tavakoli @pygmalion.com), and then click More Settings.
i. Click the Connection tab.
j. Make sure that the Connect to Microsoft Exchange using HTTP check box is selected, and then click Exchange Proxy Settings.
k. In the Use this URL to connect to my proxy server for Exchange box, type the proxy server URL that you noted in step 1d. In this example:
m. Click to select the On fast networks, connect using HTTP first, then connect using TCP/IP check box, and then click to select the On slow networks, connect using HTTP first, then connect using TCP/IP check box.
n. Under Proxy authentication settings, select Basic Authentication.
o. Click OK two times.
p. Click Check Names. When the server name and the user name are displayed with an underline, click Next. If the Windows Security windows comes up, enter your username and password and make sure Remember my credentials box is checked.
Once it is all setup you will notice that both Server and Username fields become underlined.
q. Click Next and Finish.