If your attachments disappear from your email when you hit send, follow the steps below to correct the problem.
1. Open the Control Panel.
2. Click on the Credential Manager and select the "Windows Credentials" tab.
3. Under the Generic Credentials Section, click on the arrow and click on remove for each item.
4. Log out of Outlook.
5. Log back into Outlook.
6. Send a test document to make sure your issue is fixed.