Originally Posted by Sanford Stein
Is this something I want to do or are there negative ramifications?
There's not much mail-related topics I would want to be vocal about (legally worthless sig disclaimers being the other) but this is one. Email is bound by certain rules. These rules, RFC's, make MTA's "understand" and talk to eachother (relatively) well. Once in a while some idea surfaces that will "make everything way better". Challenge/response, greylisting is one such an idea. It involves making the receivers "problem"
the problem of the sender by modifying the MTA making other MTA's to do things (stutter, echo, talk slowly, whatever else) they should not have to just to deliver the message. Out of the box most default GNU/Linux MTA's work just fine. You should not have to customise it to deal with this. Depending on if you can deal with it from a business perspective, I'd say it's their problem so let them deal with it
either by providing clear steps or whitelisting your triplets.