I diligently add all email addresses to my customer records. Obviously essential for communicating about invoices due etcc. Occasionally, I want to send offers to my list. I ask my customers in advance if they're happy to receive but have no way to indicate within Kashflow which customers want only bona fide correspondence and which ones are happy to receive marketing promotions. I need to be able to opt in on their behalf. Good for GDPR. Thank you.