You can try to find a open SMTP Server and once you are in do this:

ehlo [Your desired domain name]
rcpt to: [The recepient email]
mail from: [Your desired email, it can even be the recepients own email that makes it seem he sent it for himself]
data
[Type the email you want to send and end with a . on its own line ex

.

then it will send the email from where you want]