Today is expected to be the U.S. Postal Service’s busiest mailing day. So if you’re heading out to stand on line at the Post Office, expect to be joined by about 6 million of your friends and neighbors. 

Zy Richardson is a public relations representative for the U.S. Postal Service. To hear her talk, you and your 6 million friends are gonna have very tired arms from carrying all that stuff. “We are projecting about 607 million pieces of mail to be processed just on today alone,” she says.

She says a decade ago, post offices braced for 670 million letters and packages on this busiest day. So while total volume is down at the Post Office — first class mail has declined — the headline is the rise of packages.

Mark Schoeman is president of the Colography Group, a market research firm. He expects package shipments will go up 10 percent this holiday season, over last year.

“We’re estimating that the volume for the holiday season is gonna be around the 2.1 billion pieces,” he says, referring to packages sent through the postal service and private carriers.

Schoeman also says shipment weights are lighter than in the past. Perhaps we’re purchasing more featherweight trinkets online, like little cell phone cases.

So not everyone’s arms will be tired, after all.