[imp] sasl with relaying

[zBit]

Hello,

I've setup the smtp authentication in configuration files (config/conf.php, imp/config/backends.local.php)
but when I try to send an e-mail using bad credentials, the e-mail is sent nevertheless as the mailserver
permits relaying for the horde host. I assume that horde uses some kind of fallback so that whenever
the authentication fails it somehow bypasses the authentication completely. I would like to retain smtp
relaying. Is there any way to enforce the sasl authentication?

BR,
David