I've got a Joomla 1.5 site, for signing up user in site make it possible for the e-mail delivering system's, set up the smtp server in joomla configuration. my config is:

mailer:'smtp server'
smtp host:''
smtp user:''
smtp psw:'mypass'
smtp port:'465' 
smtp authentication:'yes'
smtp security:'ssl'

I'm not sure becuase doesn't work which is worth observing that php mail function dosen't work!

uncomment "extension=php_openssl.dll" inside your php.ini file

add exception for port 465