In MS Outlook 2019, my settings are:

Incoming:
-POP3 (not imap because it doesn't save sent emails to sent items in current pst...
and Send/Receive is disabled from Outlook/Home)
-Port: 995 (I tried others)
-Mail Server: mail.optusnet.com.au

Outgoing:
-Port: 25 (I tried others)
-Mail Server: smpt.optusnet.com.au (if set to mail.optusnet.com.au, half of emails to gmail accounts don't arrive - no error)
-Encryption: starttls (I tried others)
-Tick "My outgoing server requires authentication"