[imp] Difference between SMTP and sendmail method

[Piotr Legiecki]

Hi

I'm currently using imp3.1 and (from /etc/horde2/horde.php):

...
// What method should we use for sending mail? Valid options are
// currently 'sendmail' and 'smtp'.
$conf['mailer']['type'] = 'sendmail';
.....

What bothers me is the difference between sendmail and smpt method of 
mail sending?

It works fine, but I'd like to add https and smtp authentication soon.

Anyway currently we have 2 servers (with user accounts) with smtp 
authentication and IMP (installed on 3'thd server) works fine with them 
(we use exim). So I don't get the point about sendmail and smpt methods 
mentioned above *and* SMTP authentication im IMP.

Regards
Piotr L.