Can’t receive email or send email by mail apps like outlook, thunderbird, Mac mail and others device like smart phone, tablet or iPad. For this check your password is update properly if its not than please update. Still same issue than check VPN is not on.
Spam email issue in Bigpond
Receiving unwanted mails in BigPond account don’t worry just make them under spam and block sender email address.
Sever issue or outage issue.
Check your imap and pop settings are appropriate example (Incoming) Imap.telstra.com for imap with port 993 and Pop.telstra.com for Pop settings Port 995, (outgoing) common Smtp.telstra.com with 465 and 587.
Still is any of above issue does not resolve than contact Bigpond Support Number.

More Info: https://www.bigpondonlineservice.com/aboutus.html