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However, a way for the MTA plugin to *inform* the SA code of the envelope data reliably is needed. The recommended way to do this, currently, is to ensure that the message text passed to SA contains that relay's Received header. Adding the envelope-sender info along with the other envelope info (HELO, connecting IP, rDNS) makes sense here. – JustinMason
One would expect that SpamAssassin uses this in the blacklist_from and whitelist_from settings. One should point out the sad fact that plain standard distribution SpamAssassin 3.0.2 does not seem to use this feature at all. See bug ID #4175. – Thomas Eisenbarth