Blacklist affecting client computer?

I have a client who’s emails to other people within the same domain are getting marked as spam.

The issue I found is this (where xx.xx.xx.xx is their IP address):

3.3 RCVD_IN_PBL            RBL: Received via a relay in Spamhaus PBL  [xx.xx.xx.xx listed in]
1.3 RCVD_IN_RP_RNBL        RBL: Relay in RNBL,  [xx.xx.xx.xx listed in]

Looking in Nodeworx MTA settings I only have setup as a blacklist, so is this just some feature of SpamAssassin to check these other list?

I’ve tried delisting, but the PBL is actually accurate. It may not be a dymanic IP, but it’s just a business IP with no mail server running on it. So not sure if it will get listed in the PBL again.

First, not sure why it even cares what the end user’s IP address is when it’s an authenticating account connecting to the server to send mail out?

If the removals don’t hold, what’s the best way to work around this issue? Can I add the IP address of their office to the Spam Access Lists > Trusted Networks? Anything else?

What SPF records does the domain have? if the user is using another mailserver, it’s ip needs to be added to be added to the SPF record.