By default, QuotingBill will include all email notification sending. No delivery receipts, no tracking, and emails will go out using the @quotingBill.com domain. QuotingBill uses Mailgun as the default SMTP Provider.
Adding your own SMTP Relay will allow you to use your own domain when sending emails and also, have your SMTP Relay provider give you any kind of analytics, tracking, and delivery receipts based on their own feature list.