Outgoing mail settings on KMail

I need help on configuring my e-mail please. I am in South Africa and I am using 2 types of connections, when I am at work, i use a Telkom Leased line, when I am at home, i use Vodacom 3G. I can receive e-mail, no problem, but when I send, it doesnt want to. In what way should I configured my outgoing mail settings to allow me to send mail. I am using OpenSuse 11, with KDE 4 desktop. E-Mail client is Kmail.
Thanks

What, if any, error message do you get?

Sending failed:
Message sending failed since the following recipients were rejected by the server:
support@imaginet.co.za (The server responded: “5.7.1 <support@imaginet.co.za>: Relay access denied”)
The message will stay in the ‘outbox’ folder until you either fix the problem (e.g. a broken address) or remove the message from the ‘outbox’ folder.
The following transport protocol was used:

That is the error message which I am getting when sending.

In Kmail’s configuration for outgoing mail, have you you checked the ‘Server Requires Authentication’ box?