In hsphere you can whitelist an IP from RBL checks by using the following:
Edit/Create the file:
/hsphere/local/var/vpopmail/etc/tcp.smtp
Add the following:
#whitelist IP addresses
$IP1:allow,RBLSMTPD=""
$IP2:allow,RBLSMTPD=""
Then: Recompile via Command Line option
cd /hsphere/local/var/vpopmail/etc/
/hsphere/shared/bin/tcprules tcp.smtp.cdb tcp.smtp.tmp < tcp.smtp