Well, looks like the charter.net mailserver is claiming that the from address belongs to either a mailing list or an alias but is unable to fully verify the members.
Code:
#119:<khuon@Espresso>(pts/18)[~]% dig mx charter.net
; <<>> DiG 2.2 <<>> mx charter.net
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6
;; flags: qr rd ra; Ques: 1, Ans: 1, Auth: 3, Addit: 2
;; QUESTIONS:
;; charter.net, type = MX, class = IN
;; ANSWERS:
charter.net. 14400 MX 10 mail.charter.net.
;; AUTHORITY RECORDS:
charter.net. 14400 NS auth1.ns.charter.net.
charter.net. 14400 NS auth2.ns.charter.net.
charter.net. 14400 NS auth0.ns.charter.net.
;; ADDITIONAL RECORDS:
mail.charter.net. 14400 A 209.225.8.224
auth2.ns.charter.net. 14400 A 209.225.8.43
;; Total query time: 148 msec
;; FROM: Espresso.NEEBU.Net to SERVER: default -- 127.0.0.1
;; WHEN: Tue Dec 14 15:03:44 2004
;; MSG SIZE sent: 29 rcvd: 145
#120:<khuon@Espresso>(pts/18)[~]% telnet mail.charter.net smtp
Trying 209.225.8.224...
Connected to mail.charter.net.
Escape character is '^]'.
220 mxip14a.cluster1.charter.net ESMTP
vrfy everett717
252 ok