How can we send email server side when the author is not in netsuite?

I don't think it is possible using NS-API.

@Watz thanks, how would you do that?

Maybe you misread? It is not possible using NS-API AFAIK. You'd probably have to use some external service. (or create the author in Netsuite before you send the e-mail)

You just make an employee that you want the email to come from and assign them as the author.

confirm @Sandii... that employee can be no-licence, without "Give access"

Not sure if you were asking or confirming, but yes the employee does not need access to be the author on an email.

confirming you. We are using the same concept, virtual employees for sending bulk emails.