Please try these steps...
1. Open Microsoft Outlook.
2. Click OK to close the outscan.dll error.
3. On the Outlook menu, click on Tools and Options.
4. Click on the Other tab.
5. Click on the Advanced options button.
6. Click on the Add-In Manager button.
7. Remove the check from all of the occurrences of McAfee VirusScan Outlook Email Scanner except for one. If there is only one occurrence, uncheck it.
8. Click OK several times to close out of all of the windows.
9. Exit Outlook, and then restart Outlook and the error will not occur.