Error message 550 when sending emails

[mkcmlsed]

undefined :rolleyes:

I recently connected to broadband from dial up dodo, since then i am unable to send any emails. I receive the following messages

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was '[e-mail]'. Subject 'gerard stll missing', Account: 'dodo', Server: 'smtp.dodo.com.au', Protocol: SMTP, Server Response: '550 relay not permitted', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79

The host 'mail.bigpond.net.au' could not be found. Please verify that you have entered the server name correctly. Account: 'pop-server.bigpond.net.au', Server: 'mail.bigpond.net.au', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 11004, Error Number: 0x800CCC0D
can anyone help me.