Hi,
Just a reminder that Telstra only support SSL IMAP connections. So when configuring your mail client, make sure you set it to use SSL (port 993 for IMAP).
So for your new account, your server setting should be:
Outbound: smtp.telstra.com
(enable SSL is highly recommended, client should auto-change the port, or you can put in 465)
Inbound: imap.telstra.com
(enable SSL is required, port 993)
For your existing account, it depends where you were migrated.
If it was to Outlook, then you can use the settings on this page:
Scroll down to "Telstra email on the Outlook.com platform".
If it was migrated to the new platform, then the settings I put up above will work.