Let's perform some steps to resolve this, dmlutz.

Before doing so, here are the few possible reasons as to why you've encountered this issue. 

1. The email preference is set up incorrectly.
2. A damaged QuickBooks installation.
3. Domain admin was blocked.
4. Account security settings from your email provider.

To resolve this, let's make sure that your QuickBooks is updated to the latest release. Then, verify the settings in your Preferences menu to see if the information was correct. Also, you'll have to verify if your email is set up correctly.

Here are the steps: 

1. Go to Edit and select Preferences.
2. Click Send Forms in the Preference page.
3. Select the My Preferences tab.
4. In the Send E-mail Using area, you get an option to choose what email setup you'd like.
5. Choose Web Mail.
6. Click Add.
7. Enter Email Id and Email Provider.
8. Enter SMTP Server Details, and click OK.

Once done, you can perform the task again in sending email statements to your customer. 

I've also included a helpful article in setting up email service.

You can get back to the Community space if you need more help. Have a blissful day!