SoftEther VPN User Forum

BigPond requires that Thunderbird use SMTP Authentication when email seems to come from outside of their network, like when a VPN session is running.

Note that email will never work through proxy hosts or VPN hosts that are blacklisted, which is very likely if you are using a commercial VPN service.

With local bridging (layer 2) Bigpond sees you're client as connected directly, so sending mails should not be a problem.

If you want to sent a mail while using VPN, you should add a route to the mail server.