Came across this error when some users couldn't connect to our Solaris 10 vsftp daemon, this error was showing up in /var/adm/messages, but others were connected just fine.
Jul 21 11:20:43 ftpserver vsftpd: [ID 140027 daemon.error] warning: can't verify hostname: gethostbyname(8-221.int.cec.wustl.edu) failed
Jul 21 11:20:43 ftpserver vsftpd: [ID 913506 daemon.warning] refused connect from 172.16.8.221 (name/address mismatch)
This turned out to be caused by tcp_wrappers, you have to disable it.
inetadm -m svc:/network/ftp:default tcp_wrappers=FALSE