It should be as easy as adding: "/usr/bin/strace -ff -o /tmp/vchkpw.dump" right before "/home/vpopmail/bin/vchkpw" in the qmail-smtpd/run file.
Attempt a SMTP AUTH connection, and then send me a copy of the /tmp/vchkpw.dump file and I'll try to isolate the source of the problem.
-- Tom Collins - [EMAIL PROTECTED] QmailAdmin: http://qmailadmin.sf.net/ Vpopmail: http://vpopmail.sf.net/ Info on the Sniffter hand-held Network Tester: http://sniffter.com/