the environments: redhat7.0 + qmail-1.0.3 + vpopmail-4.9.10 + ucspi-tcp-0.88 + daemontools-0.70. after I intalled qmail1.0.3, there was no problem for sending and receiving email. then continue installing vpopmail,the whole steps in detail look like below: 1,./configure --enable-romaming-user=y --enable-default-domain=mydomain.com --enable-ucspi-dir=../ucspi-tcp-0.88; 2, make; make install-strip; 3, ./vadddomain mydomain; 4, ./vadduser myuser; 5, replace the entry checkpassword in the file /service/qmail-pop3d/run with vchkpw; the files concerned will look like below: the file /var/qmail/control/me: mail.mydomain.net the file /var/qmail/control/locals: localhost mail.mydomain.net the file /var/qmail/control/rcpthosts: localhost mail.mydomain.net mydomain.net the file /var/qmail/control/virtualdomains: mydomain.net the file /var/qmail/control/defaultdomain: mydomain.net the file /var/qmail/user/assign: +testdomain.net-:testdomain.net:501:508:/home/vpopmail/domains/testdomain.net:-:: . the file /etc/tcp.smtp: 127.0.0.:allow,RELAYCLIENT='' 129.0.0.:allow,RELAYCLIENT='' 63.108.64.5:allow,RELAYCLIENT='' :allow nothing for /var/qmail/control/plusdomain; (the user vpopmail and group vchkpw have been created before installing vpopmail) then test the pop3d service with vchkpw from the address 129.0.10.15: telnet mail.mydomain.net 110 trying 129.0.10.18... connected to 129.0.10.18. Escape character is '^]'. +ok<[EMAIL PROTECTED]> user testuser +ok pass 123 -ERR authorization failed Connection closed by foreign host. (the result was same as test launched at mail server itself) if I test the pop3d service with checkpassword from the address 129.0.10.15: telnet mail.mydomain.net 110 trying 129.0.10.18... connected to 129.0.10.18. Escape character is '^]'. +ok<[EMAIL PROTECTED]> user testuser +ok pass 123 +ok if I send email from somewhere to [EMAIL PROTECTED], the email can be delived to the directory correctly: /home/vpopmail/domains/mydomain.net/testuser/Maildir/new; now, my big problem is pop3d with the vchkpw. I don't know where I made a mistake with the vpopmail, sometimes I even thought maybe vpopmail has a bug ? I'm eager for some expert's answer, thanks a lot. hopefully lawy