SuperGraham on "[Plugin: WP Mail SMTP] open password field - please don't !"

We relay all e-mails through SendGrid which allows us to troubleshoot routing issues and check when a customer should have received a certain enquiry, etc.
When we create a new WordPress site it's done using Duplicator to reduce the time taken, and in that 'template' we have the SMTP password. I suppose the ideal option would be for each customer to have their own password in SendGrid. That would work for us, but maybe not everyone else.