This is the problem my friend is facing in his office. Someone is using an almost similar domain as my friend's company (via email). This person is posing as their company and asking them to send money with an invoice of the same format as his company uses but the only thing is different is the account details where amount should be debited while claiming that their product they ordered is out for delivery.
It seems imposter has details of clients emails, the format of the invoice the company uses and it's likely they somehow know the conversation going on between their sales office and clients.
How can I help him? Is there something that I can do or advise?