Wiktionary
mail bombs
n. (mail bomb English)
Usage examples of "mail bombs".
In fairness to the victims discussed above, mail bombs are very rare and were not the type of hazard one was normally concerned about, but the point is that these victims were concerned enough to comment on it.
Though you've likely never had reason to think about mail bombs, they are now on the menu of terroristic options - and now part of your intuition.
It could be used in mail bombs, to destroy federal buildings- any public building, actually-disrupt transportation and communication.