To update a currently configured mailbox in outlook you will need to do the following:
1. Select "File" as shown in the screenshot below.
2. Select "Account Settings" as shown below.
3. Within the list of accounts select the account you wish to modify (Make sure when selected the account shows highlighted) and then select "Change"
4. Once the "Change Account" setting page appears you can now update the Incoming and Outgoing Mail server settings as shown below:
5. To save your settings and confirm they are correct click "Next" to complete a Mail Server test as shown below:
6. Select "Close" to complete the setup. Your account settings have now been updated successfully.