please help me, a problem about mail box!!

[cool dragon]

Title: 晴朗

Hi,   I install the qmail and can start it, but when i send a mail to a user from the mail server, the maillog will say:   " delivery 3: failure: Sorry,_no_mailbox_here_by_that_name._(#5.1.1)/ "                                               and i cannot  get the mai;   If i send a mail to myself from remote site, the maillog will say nothing, and i cant get the mail too.   what's the problem, please help me! it trouble me a long time!!!