For information about the differences between Microsoft Outlook and Microsoft Outlook Express e-mail clients, click the following article number to view the article in the Microsoft Knowledge Base:
257824 OL2000: Differences Between Outlook and Outlook Express
SYMPTOMS
When you connect to Exchange Server 5.0, 5.5, or Exchange 2000 to send or receive mail in Outlook or Outlook Express, you repeatedly receive a prompt for credentials.
With Outlook Express, the following information may be displayed on the
Error tab in the
Details box:
The message could not be sent because the server rejected the sender's e-mail address. The sender's e-mail address was '<Email address>'. Subject '<Subject name>', Account: '<Account name>', Server: '<Server name>', Protocol: SMTP, Server Response: '454 5.7.3 Client was not authenticated.', Port: 25, Secure(SSL): No, Server Error: 454, Error Number: 0x800CCC78
The message could not be sent because the server rejected the sender's e-mail address. The sender's e-mail address was '<Email address>'. Subject '<Subject>', Account: '<Account name>', Server: '<Server name>', Protocol: SMTP, Server Response: '505 Authentication required', Port: 25, Secure(SSL): No, Server Error: 505, Error Number: 0x800CCC78
There was a problem logging onto your mail server. Your User Name was rejected. Account: '<Account name>', Server: '<Server name>', Protocol: POP3, Server Response: '-ERR Clear text passwords have been disabled for this protocol', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC91
RESOLUTION
If you cannot receive messages properly in Outlook Express or Outlook 2000 Internet Mail Only:
- Start Outlook 2000 or Outlook Express, and click Accounts on the Tools menu.
- In the Internet Accounts dialog box, click the Mail tab.
- Click your mail account, and then click Properties.
- Click the Servers tab, and then click to select the Log on using Secure Password Authentication check box under Incoming Mail Server.
If you cannot send messages properly in Outlook Express or Outlook 2000 Internet Mail Only:
- Start Outlook 2000 or Outlook Express, and then click Accounts on the Tools menu.
- In the Internet Accounts dialog box, click the Mail tab.
- Click your mail account, and then click Properties.
- Click the Servers tab, and then click to select the My server requires Authentication check box under Outgoing Mail Server.