Short answer: yes
Section 8 of the US Constitution allows Congress to establish post offices and post roads. Of course, once they are established you must have a set of rules to run said offices and roads.
Yes.
This is not something that Congress has to vote on. However, there is a lot of opposition to the idea- if it goes into effect, I would expect Congress to at least consider some legislation about it.
Call 9-1-1
"Snail mail" is another term for postal mail. Snail mail goes through the post office, whereas email goes through internet networks, sending much faster than postal service.
The Overland Mail Act was when the congress stopped the deliver of mail by the stagecoach service Butterfield Overland Mail Trail.
Congress passes laws about what can go through the US mail (which are signed into law by the President). Postal Inspectors, who work for the U.S. Postal Inspection Service (which falls under the Executive branch of the government) are responsible for enforcing the laws. When dangerous materials are being sent with the intention to harm someone, Homeland Security (usually via the FBI) may get involved. Illicit drugs through the mail might get the DEA involved. Illegal weapons shipments (and illegal alcohol and tobacco) might get the ATF involved.
A federal crime
You can... but I wouldn't. It goes through machines whenever you put it in a regular envelope & if its not flat... it could rip it & your key could get lost somewhere. I used to work with the 1800askusps.
Yes, you are able to legally get mailed through the mail. You are able to fill out the marriage license form and mail it through the notary of republic.
can I send hair spray through the mail
Surface mail is overseas mail that goes by ship rather than by air. Parcel mail is for parcels.
yes