Shamrock Mac

Hi, I am need help with the emails, I have just recently started using Express Invoice and I have set up 2 companies so far but what I am finding is that every time I send out an Invoice it is coming from the first business I set up and not coming from the individual companies details. Has anyone else had this and if so can I fix this so the Invoices are comg from each company's emails and not the same? Thank you