Slackware :: Cannot Send Mails To "localhost"

I am trying this with Slackware 12.0. I am trying to send mails to a user on my own machine... for example $ mail root #root or other user, it's the same (write subject and body) and it looks like the mail has been sent, by then I write mail and i've got no new mail..tried

mail root@localhost
mail root@slackware #slackware is how my machine is called (`hostname` told me :P)
mail root@127.0.0.1

and none of them worked... after hours trying to solve this, i thought i needed an smtp sever... so i started up sendmail but using mail didn't worked... i connected with netcat to port 25 and sendmail answered.. I send a mail with netcat, and sendmail said it was all ok.. but i didn't recived anything. then i realized that the mails where in queue... /var/spool/mqueue here is what sendmail tells me (i remove all the mails in mqueue and i only post 1 here)

Code:

$ sendmail -q -v
WARNING: local host name (slackware) is not qualified; see cf/README: WHO AM I?
Running /var/spool/mqueue/p61FPoll003674 (sequence 1 of 1)
slackware: Name server timeout

[code]....