Mail System doesnt work!

[crichton]

I cant get the email System working. I installed the webmail addon and it dosnt work neither. The /var/log/mail.err log says:

Sep 21 20:16:00 moyatec postfix/smtpd[31112]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:17:02 moyatec postfix/smtpd[31783]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:18:02 moyatec postfix/smtpd[32130]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:19:03 moyatec postfix/smtpd[32479]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:20:04 moyatec postfix/smtpd[486]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:21:05 moyatec postfix/smtpd[807]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:22:06 moyatec postfix/smtpd[1157]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:23:07 moyatec postfix/smtpd[1671]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:24:08 moyatec postfix/smtpd[3092]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:25:09 moyatec postfix/smtpd[3446]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:26:10 moyatec postfix/smtpd[3785]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:27:11 moyatec postfix/smtpd[4136]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:28:12 moyatec postfix/smtpd[4475]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:29:13 moyatec postfix/smtpd[4812]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:30:14 moyatec postfix/smtpd[5294]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:31:15 moyatec postfix/smtpd[5648]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:32:16 moyatec postfix/smtpd[5983]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:33:17 moyatec postfix/smtpd[6321]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:34:18 moyatec postfix/smtpd[6666]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:35:19 moyatec postfix/smtpd[7047]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:36:20 moyatec postfix/smtpd[7425]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:37:21 moyatec postfix/smtpd[7752]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:37:56 moyatec imaplogin: DISCONNECTED, ip=[::ffff:127.0.0.1], time=0
Sep 21 20:38:22 moyatec postfix/smtpd[9399]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:39:23 moyatec postfix/smtpd[9860]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:40:24 moyatec postfix/smtpd[10306]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:41:25 moyatec postfix/smtpd[10704]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:42:26 moyatec postfix/smtpd[11173]: fatal: open database /etc/aliases.db: No such file or directory
Sep 21 20:43:27 moyatec postfix/smtpd[11523]: fatal: open database /etc/aliases.db: No such file or directory

The file is there! But its emty! What could be the Problem?

HELP