If you have enabled the smtp server at horde mailer settings then you have to install the Net_SMTP package from pear.
You can check your conf.php file under config folder
One way to do this is to cat this file and grep mailer
cat conf.php | grep mailer
$conf['mailer']['params']['host'] = 'mail.example.com'; $conf['mailer']['params']['port'] = 25; $conf['mailer']['params']['auth'] = true; $conf['mailer']['type'] = 'smtp';
I was not able to send mail from the webmail, and I check the logs from apache. I saw these logs:
tail -f apache_error.log
[error] PHP Fatal error: Class 'Net_SMTP' not found in .../php5/lib/php/Horde/Mail/Transport/Smtp.php on line 271, referer: http://webmail.example.com/imp/compose-dimp.php?type=new&ajaxui=1&uniq=13123591417264
So I checked the Smtp.php file and I saw that the Net_SMTP class is required
/** * SMTP implementation. * Requires the Net_SMTP class. **/
To install the Net_SMTP with PEAR you have to
pear install Net_SMTP
After this procedure I was able to send mail through my smtp server.