When NetSuite is set up to send customers emails based on process like Workflow , yet the email status shows as SENT despite the client’s claim that they haven’t received any —not even in their spam folder—
it’s best to check with their IT Director and ask them to whitelist : @sent-via.netsuite.com
The Mails send from NetSuite are designed as per below in the domain structure:
Although optional, it is advisable to whitelist @netsuite.com as well, just in case.