Post Affiliate Pro offers a unique multi-level marketing feature that allows you to define commission structures for an unlimited number of tiers.

You can build the affiliate tree and in case an affiliate refers a new sale, you can pay any commission to his parent. Commission structure can be defined for each level, separately.

Along with the Forced Matrix feature, it could be a strong MLM feature that motivates your affiliates to search for new affiliates, which will in turn earn more commissions for them.