Research studies show:
1) Coronaviruses like SARS can INFECT YOU up to 9 DAYS in a dried state.
2) The highest risk items would be those in mylar / plastic type envelopes or packing.
3) The same risks also apply to the items contained inside the packaging.
4)"However, its infectivity is reduced more rapidly if it is deposited on porous surfaces such as cotton or paper"
5) Obviously, the faster the delivery and the closer one lives to the package sender the greater the risk.
6) There is a historic precedent of postal infection during the Spanish Flu Epidemic
Data Sources:
Human Coronaviruses: Insights into Environmental Resistance
Stability and inactivation of SARS coronavirus