How to disable sorbs in spamassassin

I notice that sorbs.net is marking GMail's IP as spam sender which causes my users not able to receive from gmail.com. I want to disable or remove sorbs.net from checking process or add more DNSBLs in order let gmail emails in.
I tried adding the following to my local.cf but no success:

whitelist_from_rcvd  *@gmail.com  gmail.com
score   __RCVD_IN_SORBS  0

I also tried to comment/delete sorbs from 20_dnsbl_tests.cf but it didn't do anything either.

Here's the log from maillog:

NOQUEUE: reject: RCPT from mail-oi0-f48.google.com[209.85.218.48]: 
454 4.7.1 Service unavailable; Client host [209.85.218.48] blocked using dnsbl.sorbs.net; 
Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?209.85.218.48; 
from=<someone@gmail.com> to=<email@domain.com> proto=ESMTP helo=<mail-oi0-f48.google.com>
Sep  3 15:03:05 server postfix/smtpd[16891]: disconnect from mail-oi0-f48.google.com[209.85.218.48]