Help smtp in qmail

[edy]

hi..... can someone help meeee i have a problem with my smtp in qmail, the smtp doesn't response for a long time. But when this problem happen we can restart the mail server and it can run normally. i check the log but no log for this problem, and when the problem occurs we check with netstat it respond for a long time too. i already check the network but no problem with that.     any body can help me pleaseeeee