Target LISTSERV version
This document concentrates on LISTSERV Version 16.0, its later "level-set" and point releases, and LISTSERV 17.0. Older versions are outdated and obsolete for a number of reasons, including fixed bugs, fixed WA vulnerabilities, and deliverability issues. Specifically, any site running a build of LISTSERV earlier than the 16.0-2017a "level set" release should be planning to upgrade, soon, as there are issues with earlier versions (particularly with the web interface CGI prior to 16.0-2017a, but also with various subsystems such as DMARC which have been fixed in later releases).
Additionally, LISTSERV sites running anything older than the latest Generally Available release (17.0, released on 9 July 2019) should strongly consider upgrading to the GA release. Release notes for 17.0 and any later "level-set" releases can be viewed at our Documentation and Manuals page.
As time goes by, this document will be revised to concentrate on the current Generally Available release.