SalesForce has a built-in field called “Email Opt Out” aka emailOptOut.
As SalesForce is a CRM, you generally plan to contact people who are leads, so opt-in may not make sense. If you want an opt-in to marketing emails (vs transactional emails) you’d likely want to use a custom field for that. Then you could email users who “opted in” to Marketing emails seperately from emails about their request.
If you’re wanting to populate a separate email marketing system, that’s outside the purpose of this plugin and something you’d likely want to connect to Salesforce directly. You could add a hook to push emails to, say, MailChimp, upon submission, but again, that’s outside of the purpose of this plugin.
TLDR;
You can do whatever you want with custom fields, but this plugin exists solely to send leads to the Salesforce API. Anything outside of that would require custom code and you may want to look at a Form Plugin with a Salesforce connector instead.
