[ delphus@netserver:~ $ ] host 200.204.201.226
226.201.204.200.IN-ADDR.ARPA domain name pointer 200-204-201-226.speedyterra.com.br
[ delphus@netserver:~ $ ] telnet mail.delphus.org 25
Trying 200.162.6.71...
Connected to mail.delphus.org.
Escape character is '^]'.
220 mail.delphus.org ESMTP
mail from: delphus@delphus.org
553 sorry, your host sender has been denied (#5.7.1)
quit
221 mail.delphus.org
Connection closed by foreign host.