RBLs enable mail admins to automatically block incoming mail based on DNS lookups. But I noticed that my MTA was again blocking Google and Hotmail completely, again due to the overly restrictive SORBS blacklist. This is inacceptable collateral damage, so I suggest you don’t use SORBS if you intend to receive mail from large-scaled customer sites. SpamAssassin still gives scores for that blacklist, but not enough to trigger a blocking by only that single list.