When a user experiences problems emailing an invoice straight from the QuickBooks Desktop application, the message QuickBooks Desktop cannot send invoice is usually generated. Numerous things, including obsolete QuickBooks software, improper email settings, email server problems, and PDF viewer issues, can cause this difficulty. Checking email preferences, updating QuickBooks, making sure the email server settings are accurate, and troubleshooting any software issues are frequently necessary steps in resolving this issue.