If a package is heavier than the prepaid label then it will usually be returned to you saying insufficient postage or sometimes it may simply be delivered to the address you shipped it too and the receiver of the package may have to pay the additional postage.
I've sometimes had a package delivered to me without proper postage and I had to pay the rest of the fee to get the package and sometimes I've had the packages that I've sent returned to me.
The mailman will pick up packages from your mailbox as long as the package has the proper postage label affixed and as long as you raise the flag up to indicate outgoing mail.
If the flag is not up the mailman likely won't pick up the package as they would assume it's mail for yourself.
You can also schedule package pickups from USPS on the USPS website.
You can drop small packages in the USPS blue mailboxes as long as they have the proper postage label on them and as long as they fit.
If the package is larger then you should take it into the post office and hand it over the counter of if they have a larger drop box for the larger packages then drop the package in there instead.
You can leave packages in your mailbox for the mailman to take as long as you have prepaid postage labels on the packages and the package fits in the mailbox.
After leaving the package in the mailbox you should be sure to put the flag up which indicates to the mailman that you have outgoing mail for them to pick up.
As long as the package has proper postage the mailman will take it and deliver it back to the post office to be sorted.
If it has the proper postage it will then be sent out to a sorting facility and delivered to the address you have it on.
You can also schedule pickups for packages at USPS website so that they know that you have outgoing packages for them.
You can mail any package including a small package from your house after weighing the package and printing a prepaid shipping label.
Once you've printed a prepaid shipping label and paid for postage you can place the small package in your mailbox for pickup.
Just make sure the postage is the correct postage with the label and leave the small package in your mailbox.
The USPS postal delivery worker will pick the package up and scan it into their system and take it back to the post office for sorting.
You can also mail larger packages from your house after paying for postage and and affixing the prepaid shipping label.
As long as it has the correct postage the package can be shipped from home.
You can also in some locations have UPS and FedEx pick up prepaid postage packages from your house or business if they come by the area.
Or you can drop off prepaid UPS or FedEx packages at drop off locations including Dollar General.
You can use the USPS website to pay for and create a shipping label, pay for postage and schedule a pickup.
You'll also need a postage label printer to print the shipping label and shipping labels that you use with your label printer.