letter bomb

letter bomb is an improvised explosive device or weapon type.

Also recorded as mail bomb; parcel bomb; postal bomb; post bomb.

In detail

Recorded constituent parts are mail item and explosive chemicals.

Sources

Each source is named with the standing the house places on it, so the evidence can be weighed rather than taken on trust.

reference work · Reputable secondary · Wikipedia
“Letter bomb”, English Wikipedia, consulted as further reading
Consult the source
reference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q384080: letter bomb
Consult the source