On Thunderbird v78+:   FIRST   On Menu go to: Edit => Account Settings   Click on your account: younrame@tpg.com.au   Select ‘Edit SMTP server’   Port: 587 (default)   Connection Security: ‘STARTTLS’   Authentication Method: ‘Normal Password’   NEXT   On Menu go to: Edit => Preferences   Select ‘General’   Scroll down to the bottom and click on ‘Config Editor’   You will get a popup ‘Here be Dragons’, click ‘I accept the risk’   Find ‘security.tls.version.min’ by scrolling down and double click on it.   A box will pop up which will probably have a ‘3’, change this to a ‘1’   Why do you need to do this?   Thunderbird supports TLS v1.2 as a minimum version ( security.tls.version.min’ = 3 )   TPG supports only:   TLS v1.1 ( security.tls.version.min = 2) OR   TLS v1.0 ( security.tls.version.min = 1 ) ... View more