Can't receive or send emails with Thunderbird
Sending of the message failed.
Peer reports incompatible or unsupported protocol version.
The configuration related to smtp.tpg.com.au must be corrected.
A moderator produced this article for Thunderbird.
You'll notice near the end that SSL is set to NONE, so all communication is not encrypted. Thunderbird v78 has deprecated SSL/TLS below TLSv1.2.
If you want to use encryption, have a look here:
Read through the whole lot but take note at the end from David1010. I don't use Thunderbird so I can't comment on it.