There are a number of ways to contact the XSF and/or its members.
If you have a general enquiry please email info (at) xmpp (dot) org.
If you want to enquire about sponsorship opportuntities please email sponsors (at) xmpp (dot) org.
Finally you can join in the many XMPP Discussions occurring on the mailing lists.
The Foundation’s postal address is:
1899 Wynkoop Street
Denver, CO 80202 USA