ZhangHuangbin: well, something was messed up in my OS -> postfix used sendmail, postfix and other MTA's was badly configured (dunno why)
i reinstalled it to fresh install (without LAMP server) and installed, everything is fine, except that every mail is rejected (NOQUEUE: reject: RCPT from mail-qy0-f170.google.com[18.104.22.168]...)
i guess it has something to do with DNS... do i have to run DNS server on my server?
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 450 450 4.7.1 <email@example.com>: Recipient address rejected: Policy Rejection- Please try later. (state 14).
ok, i added google.com into postfix-policyd's table whitelist_dnsname, and mail was delivered -> greylisting problem