postfix不能收信。。（lmtp）

darkslack

用postfix给系统用户发信是可以得，
cyrus-sasl,cyrus-imapd配置好后，telnet 也是好的
但用postfix给虚拟用户发信却不能，
/var/log/maillog:
Dec 17 15:19:37 ds postfix/lmtp[1545]: 1E52F33F60: to=<test@darkslack.com>, orig_to=<test>, relay=none, dela
y=198, delays=197/0.32/0.21/0, dsn=4.4.1, status=deferred (connect to ds.darkslack.com[/var/imap/socket/lmtp
]: Permission denied)
Dec 17 15:19:38 ds postfix/qmgr[1514]: warning: premature end-of-input on private/smtp socket while reading
input attribute name
Dec 17 15:19:38 ds postfix/qmgr[1514]: warning: private/smtp socket: malformed response
Dec 17 15:19:38 ds postfix/qmgr[1514]: warning: transport smtp failure -- see a previous warning/fatal/panic
logfile record for the problem description
Dec 17 15:19:38 ds postfix/master[1512]: warning: process /usr/libexec/postfix/smtp pid 1537 exit status 1
Dec 17 15:19:38 ds postfix/master[1512]: warning: /usr/libexec/postfix/smtp: bad command startup -- throttli
ng
Dec 17 15:19:38 ds postfix/qmgr[1514]: 21ADD33F79: to=<stats@openwebmail.acatysmoof.com>, relay=none, delay=
56974, delays=56973/1.1/0/0, dsn=4.3.0, status=deferred (unknown mail transport error)