PHP Swift mailer: Failed to authenticate on SMTP using 2 possible authenticators

[darksoon]

When I send an email with the PHP Swift mailer to this server: smtp.exchange.example.com like this:\[code\]/ Load transport$this->transport = Swift_SmtpTransport::newInstance( self::$config->hostname, self::$config->port ) ->setUsername(self::$config->username) ->setPassword(self::$config->password);// Load mailer$this->mailer = Swift_Mailer::newInstance($this->transport);// Initialize message$this->message = Swift_Message::newInstance();// From$this->message->setFrom(self::$config->from);// .. Set message etc.// Send$this->mailer->send($this->message);\[/code\]I get a strange error back\[quote\] Failed to authenticate on SMTP server with username "[email protected]" using 2 possible authenticators\[/quote\]I know for sure that the login info is correct. What can be the problem?