I don't know what response is given to the sending client when postfix puts an incoming mail into the hold queue, say because of an access table HOLD action.
At the time of actioning the hold, is sender told the mail has been delivered (250), or something else - or is no response given at all? Is there an attempt to give any info back to original sender when the mail is finally released for delivery, or deleted - which may of course be much later? (I do not allow DSN requests from strangers, if this makes any difference.)
