The Microsoft knowledge base has help about this error - see http://support.microsoft.com/?kbid=813514
Err Msg: Your Server Has Unexpectedly Terminated the Connection..., Article ID: Q194068. This describes problems with secure logon.
XFOR: Error Message: Your Server Has Unexpectedly Terminated the Connection, Article ID: Q278637. This is regarding a server-generated error. If this is being caused by a server configuration, you must to contact your ISP.
Below is a NAV offered workaround
As a workaround, you can disable email protection by following the instructions that apply to your version of NAV:
NAV 2002/2003:
1. Start NAV, and then click Options.
2. Click Email.
3. Uncheck Scan incoming Email and Scan outgoing Email.
4. Click OK.
NAV 2000/2001:
1. Start NAV, and then click Options.
2. Click Email Protection in the Options list.
3. Depending on your version:
NAV 2000 users, uncheck "Enable email protection (recommended)" and then click OK.
NAV 2001 users, uncheck the boxes that correspond to the protected email clients.
4. Click OK.
Disabling email protection does not leave your computer vulnerable to viruses and malicious software in email. It is a separate layer of protection in addition to Auto-Protect. Auto-Protect scans any incoming files, including email, as they are saved to your hard drive. As long as you keep your virus definitions up to date with LiveUpdate, and keep Auto-Protect enabled and set to scan files as they are created or downloaded, your system is fully protected.
If disabling email protection does not solve this problem, then contact your Internet provider and ask them about the information in the Microsoft documents.
