qmail-verify as used in netqmail 1.06 is prone to a mail-address verification bypass vulnerability.
https://www.openwall.com/lists/oss-security/2020/05/19/8
https://www.debian.org/security/2020/dsa-4692
https://usn.ubuntu.com/4556-1/
https://lists.debian.org/debian-lts-announce/2020/06/msg00002.html