Hello, @Calixtus.

I'll help ensure you'll be able to send your invoices successfully.

First, ensure that your email service is set up correctly to QuickBooks. For further details, you can check this article: Set up email service.

If you're getting the same problem, I suggest following the steps provided above or the steps laid out in this article to resolve the problem: QuickBooks won't accept my web mail password.

However, if the problem continues, I recommend getting in touch with our Support Team. This way, they'll be able to check and investigate this further securely.

For the support's contact information, you can check it here: Contact the QuickBooks Desktop Customer Support Team.

If you have any other QuickBooks concerns in the future, you can also read our help articles: Help articles for QuickBooks Desktop.

Keep posted if you have any other questions about emailing transactions from QBDT. I'm just here available to help!