It's no secret that Greylisting is an effective spam-fighting tool: https://portal.smartertools.com/kb/a2692/enable-greylisting.aspx

 

Unfortunately, it doesn't work when there's a Null Sender in the envelope header. Looking at a spamtrap mailbox, 5 out of the 7 spam messages that came in this morning have a null sender.

 

Another problem with this not working is that it doesn't provide a delay for the RBLs to kick in. Often the spammer's IP gets listed on the RBL, but it takes a few minutes and greylisting provides a short delay for this to work.

 

Can this be fixed in 15.x? Scoring is not a fix because many legitimate system messages have a null sender. Created a new post because this one is marked as Resolved: https://portal.smartertools.com/community/a89457/vulnerability-certain-spam-checks-dont-run-for-null-senders.aspx

 

Thanks,

Kevin