There are many active discussion venues for Jabber/XMPP developers, system administrators, and end users. These lists are all easily searchable at www.mail-archive.com.

For End Users

JUser@jabber.org email list — for discussion about use of IM clients (subscribe | archives)

For System Admins

Operators@xmpp.org email list — for discussion about day-to-day operation of the Jabber/XMPP communications network (subscribe | archives)

For Developers

JDev@jabber.org email list — for discussion about software development using Jabber/XMPP technologies (subscribe | archives)

Standards@xmpp.org email list — for general discussion about XMPP protocols (subscribe | archives)

xmpp@ietf.org email list — official list for XMPP Working Group discussions at the IETF (subscribe | archives)

For Members

Members@xmpp.org email list — official list for members of the XSF. Subscription is available for members only, but the archives can be found here.

Special-Purpose Venues

The following special-purpose mailing lists provide low-volume, high-quality discussion among developers interested in specific aspects of XMPP technologies.

IOT@xmpp.org email list — for discussion about the use of XMPP in the Internet of Things (subscribe | archives)

Security@xmpp.org email list — for discussion about security issues related to XMPP, including encryption, authentication, and spam (subscribe | archives)

All of these venues are completely free and open to any interested individual.