Where are the settings that determine the filename of invoices send via the "Merge and Send" button when creating a Message in the NetSuite UI?

AI generated answer (using internal Slack threads):

The filename of invoices sent via the "Merge and Send" button when creating a Message in the NetSuite UI is determined by the settings in the Email Preferences field of the Customer record. This setting prevails over the Set Preferences in the Transactions tab. If you want to default the attachment to PDF, you can create a Workflow on the Customer record to set the Field Value to PDF in the Email Preference field. This way, when you manually send invoices to customers, the format will always be PDF. Alternatively, you can set your own user preference to PDF. This will make NetSuite send PDF attachments by default instead of HTML body email for sales orders. Please note that these changes might affect other processes like campaigns, so it's important to test thoroughly before deploying. ****** Disclaimer: This response was generated by an artificial intelligence assistant based on previous conversations from multiple Slack channels, and may contain inaccuracies or mistakes. ******