Question : Configure SMTP relay

Hi,

I am writing an application to send an email to a particular email address.  the problem I'm having is that I can send an email to anyone within my domain eg. [email protected], but as soon as I try sending to send to [email protected]m. I get the error message :
550 5.7.1 Unable to relay for [email protected]m.  Can anyone help?

Answer : Configure SMTP relay

Add the IP of the server trying send these emails to that list above the "allow all computers which successfully authenticate to relay...." checkbox.