Good morning Astray, Windows 10 and Office suite including Outlook 2016 can throw up some curly ones at times. For the most part it's OK, I personally rely on Outlook 2016 having used Outlook for years from one version to another.
You're using the auto setup which can be problamatical to setting up, try manual configuration, manually entering the details for your main email account etc. then adding manually your Telstra/Bigpond account.
If you take a look at the following link, Telstra's Ben shows the process etc.: https://crowdsupport.telstra.com.au/t5/Telstra-and-or-BigPond-Email/Setting-up-Bigpond-email-in-Outlook-2016/td-p/525144
