Well, I was not between her and the mailman, but I will remember that in the future. I'm not sure if she thinks it is her job to "protect" us. Remember, Dallas is afraid of everything/everyone.Down/stays are advanced obedience work and takes lots and lots of practice. You 'proof' the down/stays during training with low distractions....then medium...then high (mailman is high).
There is another element to this training. She somehow thinks it's her job to take care of the mailman. You teach her that it's not her job by getting between her and the mailman....showing her that you're handling the 'problem'. Make her back-up slightly...that tells you that she got the message. Eventually, of course, you'd like her to just go directly to her mat or rug and hold the down/stay when the mailman comes.
Unfortunately no, he does not come at the same time every day, which is annoying.Does the mailman come at the same time everyday? If he does, can you just crate her or otherwise contain her? Or does this happen when anyone comes up to the house?
We could crate her if we knew when he'd be coming each day, but then she wouldn't learn not to go bonkers when he/she comes. On the other hand if we did crate her, my house wouldnt' get destroyed