SpamHaus lists IPs to blocks, not ports.

Sure but from your link

>The PBL detects end-user IP address ranges which should not be attempting to directly deliver unauthenticated SMTP email to any Internet mail server. All the email originated by an IP listed in PBL is expected to be submitted - using authentication - to a SMTP server which delivers it to destination

Means in practice port 25 (unauthenticated) and port 587 (authenticated)