I've read on argosoft.com that it would be possible sending email using the HTTP protocol - where can I find info about it?
I'm looking for a way to send a personalized newsletter off my server without putting heavy traffic on my web server. Would this be possible?
You cant. smtp or imap. At best you can have an http server which accepts mail and then talks smtp/imap with some mail server. Why do you think http would be less overhead? In fact you don't have to increase the load on your webserver to send mail from your webserver domain. If the newsletter isn't too frequent you could simply have someone send it from any mail client.
If you want to automate. There's a php function too.http://php.net/manual/en/function.mail.php (also for java and perl)