Monday marked the busiest mailing day of the year, with more than 800 million pieces of mail processed.
But what if you still need to mail your holiday cards or packages?
Hundreds stood in lines at the Jefferson City post office Monday to mail-off their Christmas cards and gifts.
Jefferson City's postmaster said Monday is the recommended day guaranteed delivery by Christmas.
"Any other day later this week you're taking a chance it won't make it there by Christmas. So today's the day you want to mail it, Jefferson City TMs Postmaster Don Knoth said.
Knoth said if you missed Monday TMs mailing frenzy, you could chance it on Tuesday.
"There are some more play days with it. You can mail them on Tuesday, Knoth said. Three days is probably the maximum right now because if you go coast to coast it would be the three day part."
The USPS said it's still a good idea to use priority mail on Tuesday to make sure it arrives on time.
On Wednesday you'll need to pick "express mail" to get it there before Christmas, and on Thursday, you could still try express or go to FEDEX or UPS and try overnight delivery.
Also don't forget to package your gifts correctly.
"Things that are really breakable they need to package very carefully. They should pack the item with newspaper, tissues, or star foam, Knoth said. But it the item inside needs to be packaged so that it's not touching the package outside."
Knoth also said to not mail cash in those greeting cards because it could easily get lost, and not to forget your return address in case the post office needs to return it to you.
To save time, the post office recommends using their online options to buy postage or their automated machines in the lobbies of the post office.