I hate this as well.....the email request ALWAYS seems to go into the customer's spam folder. And many times business security filters reject the message altogether. Such a pain. We love using shopify payments because of the low processing rates, but its such a pain to collect payment from customers who aren't purchasing through our website. We used paypal payments pro for a while and we could literally put a payment portal on our website that customers could access and send us a credit card payment for any amount. It was just a simple form they fill out and the funds are processed and posted. Having to create a draft order, send the invoice, tell the customer to check their spam folder, then click the link to process payment is such a PAIN. Come on Shopify, you can do better. Make an easy to access payment portal for businesses to integrate into their website, without any link to a shopping cart or draft order. PLEASE!!!