Hi, Cory. Since you've already tried the troubleshooting steps in the QuickBooks support article and the problem persists, we believe the issue may not be with QuickBooks. I'll explain more details below and provide a recommended solution for this recurring email-sending problem.
If you've completed the troubleshooting steps and the issue persists, the problem likely lies with your Office 365 version rather than QuickBooks. I recommend contacting Microsoft directly about this problem. They will provide you with guidance on how to fix the issue.
Moreover, here's a guided resource on how you can email your sales forms or invoices to your customers by sending them individually or as a batch or saving them when you're ready: Email sales forms, invoices, and statements in QuickBooks Desktop.
Additionally, if you want to personalize emails for your customers or vendors, check out this guide on creating email templates with custom subject lines: Create custom email templates in QuickBooks Desktop.
If you encounter any more difficulties with QuickBooks Desktop's invoice emailing feature, please let me know by replying to this thread. I'm here to offer continued support.
