Mail for domain failed! : Missing file to open at main::../web-lib-funcs.pl line 4928 at ../web-lib-funcs.pl line 823.
System is Debian Sarge, running sendmail. No errors in /var/log/mail.log upon startup about Sendmail misconfiguration. Virtualmin doesn't gripe when it checks it's configs. I've even symlinked local-host-names to sendmail.cw just in case.