hmail & roundcube & websitepanel: Why emails go to spam instead of inbox?

view story

http://serverfault.com – i installed hmail and roundcube in windows server 2008-r2 and configured web site panel to work with hmail. after sending mails with roundcube all mails go to the spam folder instead of inbox. i buyed that domain some days ago and it’s new! also i checked my ip address from here : http://www.spamhaus.org/lookup/ and it did n’t find any block list! what did i do wrong and how can i fix this problem? i have my own vps and can edit my dns server. i had created some emails some months ago and there was no problem about them. but now i really do n’t know what is going on about new cre (HowTos)