Without knowing the error in Outlook, try turning on SMTP authentication in the connection properties; also that your email userid and password are set in properties. Consider using STARTTLS/TLS for security.
For Thunderbird, to check out basic settings, set Authentication to None (or whatever disables SSL/TLS). The username is whatever you use in Post Office.
BTW, what is in the "Advanced config" section?
You can then put security back on. There is an issue with TB v78 when used with TPG mail. TB rejects the TLS version used by TPG unless some customisation is done in TB.
Look at this thread, the post by david1010, describes the changes for secure operation.
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