Mailserver

Hi, I builded a webside with nginx mariadb shopware and now i want to add a mail server so my shopware can send mails.this is only a test server so it is not online. i use Ubuntu 12.04 LTS as a VM. i installed nginx with apt-get install not with ./configure. now the problem is i cant use the mailserver and i dont know how to add it. i am pretty new to that stuff so i dont understand everything yet some help would be nice.

Thanks

EDIT: everything else is working, shopware does not have any errors, only that i cant send any mails.