If you receive:
Event ID: 4183
Source: MSExchange IMC
Category: SMTP Interface Events
Authentication attempt (AUTH LOGIN) from hostname as ntdomain\userid failed: LogonUser() call failed with error: Logon failure: unknown user name or bad password.
You have entered incorrect logon credentials AND you have the client configured to send credentials for the outgoing mail server.
If the Exchange server's IMS does not require authentication from the hosts or clients that connect to it, the client does not need to be configured to require authentication. To check if the IMS requires authentication:
1. Use the Exchange Server Administrator to open the IMS properties.
2. Click the Connections tab.
3. Inspect the Accept Connections area:
If From any host (secure or non-secure) is selected,
the client doesn't need to be configured to required authentication on the outgoing mail server.
If Only from hosts using Authentication is selected,
the client does need to be configured to required authentication on the outgoing mail server.
To check how the Outlook Express client is configured, click Accounts on the OE Tools menu. Select the mail account and click Properties / Servers tab / Outgoing Mail Server area:
If IMS requires authentication,
check the My server requires authentication box.
Click Settings and enter the proper logon information.
If IMS doesn't require authentication,
do NOT check the My server requires authentication box.