This guide addresses Exim email authentication challenges, specifically focusing on scenarios where email sending functionality is disrupted after an Exim upgrade. If you’re experiencing issues with Exim not authenticating for sending emails, this article will provide insights and solutions to help you resolve the problem.

Understanding the Problem

The problem arises when Exim, after an update, fails to authenticate outgoing emails. While email reception and local mail delivery might work, remote email applications encounter authentication errors.

Troubleshooting Steps

Analyzing Error Logs

The provided error logs indicate several potential issues:

• Incorrect Authentication Data: This suggests a problem with the username, password, or authentication mechanism.
• TLS Errors: These errors point to potential issues with the TLS configuration or certificates.
• Connection Closed by Foreign Host: This could be due to a firewall blocking the connection or an issue with the Exim configuration.

Verifying Exim Configuration

The Exim configuration appears to be set up correctly for authentication and TLS on the necessary ports. However, further investigation is needed to pinpoint the exact cause of the errors.

Potential Solutions

Several solutions can be explored:

Solution 1: Check Credentials

Ensure that the username and password used for authentication are correct and that the user has the necessary permissions to send emails.

Solution 2: Review Authentication Mechanisms

Verify that the authentication mechanisms supported by Exim are compatible with the email client.

Solution 3: Inspect TLS Configuration

Examine the TLS configuration in Exim to ensure that the correct certificates are being used and that the cipher suites are compatible with the email client.

Solution 4: Investigate Firewall Rules

Check if any firewall rules are blocking outgoing connections on ports 587 or 465.

Solution 5: Test with OpenSSL

Use OpenSSL to connect to the Exim server on ports 25 and 587 with the -starttls smtp option to test the TLS handshake and identify any certificate issues.

Additional Tips

• Review Exim Documentation: The Exim documentation provides comprehensive information on configuration options and troubleshooting.
• Seek Community Support: Online forums and communities dedicated to Exim can offer valuable insights and assistance.
• Consider Professional Help: If the issue persists, consider seeking help from a qualified system administrator or Exim expert.

By systematically troubleshooting and implementing the suggested solutions, you can effectively resolve Exim Email Authentication errors and restore email sending functionality.

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