Installing your newly created Office 365 Exchange Online mailbox on Outlook can really be a very easy job, especially with the Autodiscover feature. Most of the times you only need to enter the name of the user, the email address as you configured it in Office 365 and then the password. Outlook will Autodiscover the server and authenticate automatically and setup Outlook for you. This is how easy it is with Outlook 2013, but if you use older versions of Outlook you can run into some issues and sometimes after the Autodiscover process, Outlook will get stuck at the connect to Outlook.office365.com Password Prompt. This password prompt will pop up and it will look like you have the wrong password as it will keep going back to the Password Prompt.
The main reason for this is because Microsoft Outlook is not Up-to-Date with the latest Windows Updates. The easiest way to make sure that all your Windows Updates has been installed is to go to START -> ALL PROGRAMS and click on WINDOWS UPDATES. Select Check for Updates on the left and wait for Windows to install all outstanding updates.
Sometimes you do not have the time to sit and wait for Windows Updates to install automatically so you want to only install the Windows Updates to enable you to install the Office 365 email mailbox. Here are the Updates and Service Packs that you need to install for each version of Outlook to enable it to Autodiscover your Office 365 mailbox without any issues.
Take note that Office 365 Exchange Online only works on Outlook 2007, Outlook 2010 and Outlook 2013.
Microsoft Office 2007:
Microsoft Office 2010:
Microsoft Office 2013 was developed with Office 365 Exchange Online and Autodiscover in mind so Office 2013 should work straight away after installation.
After you installed the above updates and service packs for the specific version of Office you have, you should not experience any further issues with the connect to Outlook.Office365.com Password Prompt.