This document concentrates on LISTSERV Version 16.0, its later "level-set" and point releases, and LISTSERV 17.0 and 17.5.  Older versions are outdated and obsolete for a number of reasons, including fixed bugs, fixed WA vulnerabilities, and deliverability issues.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 (17.5, released on 20 Nov 2024) should strongly consider upgrading to the GA release.  Release notes for LISTSERV 17.5 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.