How to allow open relay for a particular IP in QmailToaster

Open the file /etc/tcprules.d/tcp.smtp
Add the IP,
IP:allow,RELAYCLIENT=""
Save the file

tcprules /etc/tcprules.d/tcp.smtp.cdb /etc/tcprules.d/tcp.smtp.tmp < /etc/tcprules.d/tcp.smtp

This will allow relay from that IP.

Do you need to test this?

[root@bkserver1 ~]# telnet mailserver 25
Trying IP...
Connected to mailserver (IP).
Escape character is '^]'.
220 server.com - Welcome to Qmail Toaster Ver. 1.3 SMTP Server ESMTP
mail from:user@gmail.com
250 ok
rcpt to:user@yahoo.com
250 ok
data
354 go ahead
subject:This is a test
to:user@yahoo.com
from:user@gmail.com
This is the msg body of test
.
250 ok 1375419193 qp 22691
quit
221 server.com - Welcome to Qmail Toaster Ver. 1.3 SMTP Server
Connection closed by foreign host.
[root@bkserver1 ~]#