I'll outline below how to fix issues when you encounter an incorrect password when sending emails to your customers, Karen. 

Before we start, ensure that your QuickBooks Desktop is updated to the latest release. Then, email a test transaction to yourself to check if the error persists. 

If you still get the same error, access your online email service. Review your settings and filter preferences, as they may be blocking your QuickBooks emails unintentionally from coming through.

The steps to resolve the issue may vary depending on the specific email service that you are using. 

If you're using Gmail, review the app preferences: 

1. Enable access for less secure apps. You can also set access preferences for specific apps. 
2. Return to QuickBooks and attempt to send a test email transaction. 
3. If you still can't send emails, consider turning off the 2-Step Verification feature for your Gmail account.

For Yahoo! Mail, review the security settings: 

1. Head to your Yahoo Account Security page.
2. Enable Two-step verification and Allow apps that use less secure sign-in features. 
3. Go back to QuickBooks and attempt to send a test email transaction. 

 
If you still can't send emails, consider using Yahoo's third-party app passwords tool, which generates a random password for connecting QuickBooks. This process only needs to be completed once.

Please know that the password will expire after sending 12 invoices or transactions if you're batch-sending emails. You'll need to generate a new third-party app password to continue. 

1. Obtain a password, then return to QuickBooks.
2. Send a test transaction to yourself. 
3. Enter the third-party app password in the Password field and select OK.

Additionally, for other email services such as Hotmail and AOL, review the security and filter settings and create exceptions or rules to prevent QuickBooks from being blocked. 

Once done, check your antivirus settings and refer to Step 3 in this article for more detailed information: Fix webmail password issues in QuickBooks Desktop. 

If the issue persists after following all the suggested steps, I recommend contacting our technical support so they can further investigate this matter. 

For future reference, you can visit these resources to manage your sales forms, such as invoices:

• Use and customize form templates. 
• Record an invoice payment. 
• Customer, job, and sales reports. 

The following information and steps should enable you to email your invoices seamlessly, allowing you to send a copy of the transaction to your customer for updates. I'm always here to help anytime you need additional assistance with this. Stay safe, and best wishes!