A place to keep some notes....
Guide to qmail, vpopmail and qmailadmin setup on FreeBSD
So I found a great page on setting qmail up on OS X.... with one problem... it destroyed the NetInfo database that keeps user information. Fortunately I was logged in as root and could use this procedure to recover.
1. "ls -l /var/backups" – this prints a list of everything in the backups directory. It should respond with something like:
  total 40
  -rw-r--r-- 1 root wheel 19001 Aug 4 03:15 local.nidump
The date on the file (in this case "Aug 4 03:15") indicates when the backup was made. If it's not from a time when the computer was working right, or if the response doesn't list a file named "local.nidump" (e.g. if it simply gives you the localhost# prompt without printing anything first), you don't have an appropriate backup, and these instructions won't work for your situation. Sorry.
2. "cd /var/db/netinfo" – this gets us to the directory where the live NetInfo databases are kept.
3. "mv local.nidb local.nibad" – inactivate the damaged database by giving it an invalid name.
4. "nicl -raw local.nidb -create" – build a nice clean (empty) replacement database in its place.
5. "nicl -raw local.nidb -create /users/root uid 0" – for one of the later steps, we need the root user to exist in NetInfo, so create it now.
6. "niload -r / .
Notes: be careful to use "<", not ">". ">" will erase your backup file. Also, be patient; it can take a minute to rebuild the entire database. But if it takes more than 10 minutes or so, something probably went wrong, and you may need to start over.
which is modified from this procedure.