Thanks anyway for trying to help me!
YEah, it looks like it is set up to only use the included mail-function. Normally this is fine but when you have pig-headed

sys-admins that don't want to config sendmail on the server (it's a Intranet BTW) then you are out of luck since the config of PHP only works with SMTP when you are on a Windows server.
I actually kind of fixed it by digging up a SMTP-class in PHP that I've been using before. Then I went into every wwwthreads hp-file and looked for
$mailsend = mail(" etc.
and then substituted it with the smtp-class line and it looks like it works

. It took a bit of time and I haven't tested every mail-feature but at least I got the initial password mailed to me

.
Best regards
Björn