Yes, please read us the logs.
You can get the most recent log messages with:
tail /var/log/mail.log
Also, have you configured postfix yet?
You can do so with:
sudo dpkg-reconfigure postfix
This should give you a nice user interface to help configure your server.
This is what i get with the tail /var/log/mail.log command
Aug 18 11:16:31 miningfarm postfix/master[772]: warning: /usr/lib/postfix/local: bad command startup -- throttling
Aug 18 11:17:31 miningfarm postfix/local[1601]: fatal: main.cf configuration error: mailbox_size_limit is smaller than message_size_limit
Aug 18 11:17:32 miningfarm postfix/master[772]: warning: process /usr/lib/postfix/local pid 1601 exit status 1
Aug 18 11:17:32 miningfarm postfix/master[772]: warning: /usr/lib/postfix/local: bad command startup -- throttling
Aug 18 11:18:32 miningfarm postfix/local[1647]: fatal: main.cf configuration error: mailbox_size_limit is smaller than message_size_limit
Aug 18 11:18:33 miningfarm postfix/master[772]: warning: process /usr/lib/postfix/local pid 1647 exit status 1
Aug 18 11:18:33 miningfarm postfix/master[772]: warning: /usr/lib/postfix/local: bad command startup -- throttling
Aug 18 11:19:33 miningfarm postfix/local[1707]: fatal: main.cf configuration error: mailbox_size_limit is smaller than message_size_limit
Aug 18 11:19:34 miningfarm postfix/master[772]: warning: process /usr/lib/postfix/local pid 1707 exit status 1
Aug 18 11:19:34 miningfarm postfix/master[772]: warning: /usr/lib/postfix/local: bad command startup -- throttling