DENVER (CBS4) – Monday was the busiest day of the year for the post office as folks got their holiday packages in the mail.

In Denver the main processing center moved about 200,000 parcels and nearly three million letters on Monday. Adding to the shipping mayhem is “Free Shipping Monday,” where many online retailers offer no-cost mailing.

4 On Your Side Money Saver Suzanne McCarroll took a look at the deadlines and the cheapest ways to ship presents.

There were packages and boxes going in every direction on the five miles of conveyer belts at the regional postal center in Denver.

“Today is our busiest day for incoming packages, letters, parcels,” David Rupert with the U.S. Postal Service told CBS4. “This is kind of the heaviest day we have.”

Rupert said two million packages will go through there this week. McCarroll found many people dropping of packages to be shipped out on Monday.

“Christmas toys to my niece and her new son,” one woman said.

RELATED: Colorado Couple Behind ‘Free Shipping Day’

Trunks filled with outgoing presents are costly.

“I have so many packages I can’t afford to pay the priority to get them there in time,” another woman said.

The folks at Cheapism.com recently did a survey comparing the cost of FedEx, UPS and the U.S. Postal Service.

“We looked at different weights and we found that the post office is over 50 percent cheaper than FedEx and UPS,” an official at Cheapism.com said.

(credit: CBS)

On a five-pound package from New York to Chicago, FedEx charged $13.95 and UPS charged $15.50. The post office tab for the same package was just $10.

Tuesday is the last day for most international shipping for Christmas arrival, Thursday is the last day to send first-class mail for Christmas arrival, and Friday is the last day to send priority mail for Christmas arrival. Visit the U.S. Postal Service website for a list of important holiday deadlines.