I normally just use the mail function the normal way, but how do you send an email using SMTP, or IMAP and what are the advantages? I see that phpBB uses the SMTP way. I have noticed sometimes when I send an email the normal way it will end up in my junk box, is there any way I can send an email from my server, actually from one of my email accounts on my server, so that it doesnt fail.
the mail function uses SMTP by default (see php.ini).
In order to use IMAP, you'd need to a) run an IMAP server or a mail server with IMAP capabilities, and b) you need to use the IMAP functions. (see php.net)
What email client are you using? outlook? webmail? If it's outlook then either you or someone else has set the mail client to automatically put any email from your domain to the junk box.