Hello garywchen,
With QuickBooks Online, you can create professional invoices and send them to your customers in a few easy steps. QuickBooks Online is a cloud based service that uses dedicated technologies to ensure the safety and security of your information.
When you send an invoice or any other document straight from within the program, it will be safely delivered through QuickBooks dedicated email service. Your customer will see your company name in the "from" field and the subject line. The default email address cannot be changed to a personal one.
If you wish to use your own email, you can download the document in PDF format and attach it to an email using your personal email software. Here's a community article on how to download and save invoices, other sales forms, and statements as PDF: https://quickbooks.intuit.com/community/Help-Articles/Download-and-save-invoices-other-sales-forms-a....
Reach out if you have any other questions.
