Error Message: An Unknown Error Has Occurred

• Microsoft Outlook Express version 4.0 for Windows 95

SYMPTOMS

When you attempt to send a message in Outlook Express, you may receive the following error message:

   An unknown error has occurred. Account: <acct>, Server: <srv>,
   Protocol: SMTP, Server Response: '501 Invalid domain name', Port: 25
   Secure(SSL): No, Server Error: 501, Error Number: 0x800CCC63

CAUSE

This behavior if either of the following conditions exists:

• The Domain Name Service (DNS) host name or the DNS domain name specified in the Transmission Control Protocol/Internet Protocol (TCP/IP) properties contains invalid characters.
• There is a problem with your Internet service provider's (ISP) Simple Mail Transport Protocol (SMTP) server. This is the server that is used for outgoing mail.

RESOLUTION

To resolve this issue, follow the steps in the appropriate section below:

DNS Host or Domain Name Contains Invalid Characters

Verify that the DNS host name and the DNS domain name contain only valid characters. Valid characters for the DNS host name and the DNS domain name are letters (A-Z), numerals (0-9), and the hyphen (-). The period (.) is also a valid character when it is used as a separator. For example:

   ab12-3.com

1. Click Start, point to Settings, click Control Panel, and then double- click Network.

2. On the Configuration tab, click TCP/IP, and then click Properties.

3. Click the DNS Configuration tab.

4. In the Host box, verify that the name contains only valid characters.

5. In the Domain box, verify that the name contains only valid characters.

6. Click OK, click OK again, and then click Yes if you are prompted to restart the computer.

Problem with SMTP Server

To determine if there is a problem with your ISP's SMTP server, wait for a period of time, and then try to send the message again. If you still receive the error message, contact your ISP.