If you are encountering the error "Outlook cannot log on" when trying to email from QuickBooks Desktop, here are some troubleshooting steps you can follow to resolve the issue:

Check Outlook compatibility: QuickBooks Desktop requires a compatible version of Outlook to be installed on your computer. Ensure that you have a supported version of Outlook installed, and it is set up and configured correctly with your email account.

Update QuickBooks Desktop: Make sure you are using the latest version of QuickBooks Desktop, as older versions may have compatibility issues with Outlook. You can check for updates by going to the Help menu > Update QuickBooks > Update Now.

Check Outlook settings: Verify that your Outlook settings are correctly configured. Ensure that your email account is set up and working properly in Outlook, and that you are able to send and receive emails without any issues.

Repair QuickBooks installation: If QuickBooks Desktop is not installed correctly or some files are missing or corrupted, it may result in issues with emailing through Outlook. You can try repairing the QuickBooks installation by going to the Control Panel > Programs and Features > QuickBooks > Uninstall/Change > Repair.

Set Outlook as default email client: Ensure that Outlook is set as the default email client on your computer. You can do this by going to the Control Panel > Default Programs > Set your default programs > Select Outlook from the list > Set this program as default > OK.

Disable antivirus or firewall: Sometimes, antivirus or firewall programs can interfere with the email functionality of QuickBooks Desktop. Temporarily disable any antivirus or firewall programs on your computer and check if the issue persists.

Re-create Outlook profile: If the issue persists, you can try re-creating your Outlook profile. This involves creating a new profile in Outlook and setting it up with your email account. Instructions on how to create a new Outlook profile can be found on the Microsoft support website.

Greetings,
Peter