I got a patch for horde-passwd to enable crypt-md5 http://article.gmane.org/gmane.comp.horde.sork/1114/ match=passwd+vpopmail
If it links to libvpopmail, you need to recompile it after installing vpopmail 5.4.0.
If it still doesn't work, post a bug report on vpopmail.sf.net, and (hopefully) one of the developers will find time to look into it.
-- 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/