Roundcube SMTP Error (250): Authentication failed

Recently while trying to install roundcube I am stuck with the error “roundcube SMTP Error (250): Authentication failed”.

With the error the clear hint is there should be some issue with SMTP setting, so I checked all SMTP settings and I had bit doubt on following settings.

$rcmail_config['smtp_user'] = '%u';

$rcmail_config['smtp_pass'] = '%p';

After doing some experiments with my file following tweaks are worked for me.

$rcmail_config['smtp_user'] = '';

$rcmail_config['smtp_pass'] = '';