define('PLUGINS', 'auth_ldap, mailer_smtp, note');

The above enables the SMTP plugin and the email settings (above) set the SMTP credentials.

With these both, there is no reason for ttrss to use sendmail. How are you testing this btw? Is this the digest feature?

I've v1.25.0 package and yes, config.php appears exactly as you described.

I double checked in config.php using the new fantastic FileManager

Let me know if I can do other checks to fix this problem.

Thank's a lot!

Can you check the SMTP settings in /app/data/config.php ? It should have a section like this:

    // *********************************
    // *** Email and digest settings ***
    // *********************************

    define('SMTP_FROM_NAME', 'Tiny Tiny RSS');
    define('SMTP_FROM_ADDRESS', getenv('CLOUDRON_MAIL_FROM'));
    // Name, address and subject for sending outgoing mail. This applies
    // to password reset notifications, digest emails and any other mail.

    define('DIGEST_SUBJECT', '[tt-rss] New headlines for last 24 hours');
    // Subject line for email digests

    define('SMTP_SERVER', getenv('CLOUDRON_ENV_SMTP_SERVER') . ':' . getenv('CLOUDRON_MAIL_SMTP_PORT'));
    // Hostname:port combination to send outgoing mail (i.e. localhost:25).
    // Blank - use system MTA.

    define('SMTP_LOGIN', getenv('CLOUDRON_MAIL_SMTP_USERNAME'));
    define('SMTP_PASSWORD', getenv('CLOUDRON_MAIL_SMTP_PASSWORD'));
    // These two options enable SMTP authentication when sending
    // outgoing mail. Only used with SMTP_SERVER.

    define('SMTP_SECURE', '');
    // Used to select a secure SMTP connection. Allowed values: ssl, tls,
    // or empty.