The only problem using using qmail with a postgres patch and authenticating against the OpenACS database is that you either have to modify the postgres patch (and require people to patch qmail) to use the OpenACS tables and create another table (with most likely duplicate information) in OpenACS. Then if the person would rather use EXIM, Sendmail, or Postfix, they are a bit out of luck. You would also have to authenticate using POP3 and IMAP, they you need to patch those utilities to also use postgres.
My thoughts is that for webmail is that we would want to be a mail server independant as possible and if OpenACS is going to use used for authentication, they we would want the mail controlled by OpenACS instead of attempting to share data out of the database to other servers and potentionally other servers.
