Let me route you to the right support, @jimparker.
You'll have to go to Billpay.com.This way you can edit the email address of your Vendor. Just click on the My Settings link in the header of the main bill pay page.
Also, here's an article for the frequently asked questions about the Online Bill Pay for QuickBooks Online. For the complete topic list, you can open this link:
Bill Pay for QuickBooks Online.
I'm still here if you have additional questions. Take good care.
