A number of clients have had issues sending mail through their website mail server if they have Bigpond as their ISP.
Bigpond block the standard ports used for outgoing mail, and as such you need to check that you have your Outgoing Port set to 587, and SSL enabled for outgoing mail only. If prompted to choose between TLS, SSL or Auto, select Auto.
Make sure that you also have select “My outgoing server requires authentication” and have it use the same login settings as your incoming mail server.
See the following guides if you need help for your specific email application: target=”_blank” rel=”nofollow”> http://www.24hourwebhostingsupport.com/email/