Roundcube cannot send emails: SMTP Error 454

Symptoms

• Emails cannot be sent via Roundcube due to the following error:

  PLESK_ERROR: SMTP Error: Authentication failure: Invalid response code received from server (Code: 454)

• The following warnings appear in the /var/log/maillog :

  CONFIG_TEXT: Dec 20 22:13:01 postfix/smtpd[28890]: warning: SASL authentication failure: no secret in database
  Dec 20 22:13:01 postfix/smtpd[28890]: warning: localhost[::1]: SASL DIGEST-MD5 authentication failed: authentication failure

Cause

Broken Postfix configuration.

Resolution

Reinstall Postfix by switching to Qmail and back to Postifix:

• via Plesk Installer:

  1. Go to Plesk > Tools & Settings > Updates and Upgrades > Add/Remove Components > Mail hosting > SMTP servers ;

  2. Select Qmail mail server:

     

  3. Click Continue to start the installation;

  4. When the installation is completed, click OK ;

  5. Go to Add/Remove Components > Mail hosting > SMTP servers ;

  6. Select Postfix mail server:

     

  7. Click Continue to start the installation;

  8. When the installation is completed, click OK .

• via Command Line Interface (CLI):

  1. Connect to the server via SSH;

  2. Execute the following commands:

     # plesk installer --select-release-current --install-component qmail
     # plesk installer --select-release-current --install-component postfix