SOLDIERX.COM Nobody Can Stop Information Insemination

I need an expert insights on this.

we have a go daddy hosted exchange server, this scenario is that we communicate regular with company and last week the company made changes to our account from an email sent from us. I found out the email was spoofed as the header was from our email address but underline using a @usa.com email.

its like the receiver never got our actually email but only that of the spoof-er with the added instructions.

I need help understand this.

thanks