I hadn't heard that QMail was no longer maintained, but imo it was never a reasonable option.
I don't know why you would object to Postfix - it's a fine MTA - but the only real alternatives are Exim and Sendmail - and I wouldn't bother with Sendmail. Either Exim4 or Postfix are available as binary packages for both Ubuntu and Redhat and have hooks for AV,spam scanners and RBL