From Headers in Email Can Be Rewritten
If you do not complete the Procedures to Set Up DKIM for the First Time in Your Account, by default, the From header on email you send from NetSuite will be rewritten. When the From header is rewritten, the original email address is moved to the display string, and the SMTP-related email address refers to netsuite.com. For example, an email from jsmith@example.com would be rewritten to jsmith@example.com <system@sent-via.netsuite.com>. What your recipients will see as the sender of the email depends on the email client in use at the recipient’s site. Some recipients will see the original email address with the modified <system@sent-via.netsuite.com> From header. Some recipients may not see the original email address at all.