Washington ? The Postal Service expects to handle 20 billion pieces of mail between Thanksgiving and Christmas, up slightly from last year, the agency said Monday.

“It’s a good time of year for us, we look forward to this time of year,” Postmaster General John Potter said.

While the overall total averaged out to 670 million items per day, the peak mailing day is expected to be Monday, Dec. 20, as people send out cards the weekend before Christmas. Mailings could jump to 850 million items that day.

The busiest delivery day is expected to come two days later.

Mailing tips include wrapping parcels securely, printing the return and recipient’s addresses clearly and never guessing the ZIP code. People can request ZIP code information online at www.usps.com or by calling (800) ASK-USPS.

For military mail, the suggested deadline to send material via Parcel Airlift is Saturday. Priority mail can be sent until Dec. 11 to military addresses beginning with the ZIP 093.

For domestic packages the post office says to switch from parcel post to Priority Mail on Dec. 14 and to Express Mail on Dec. 23.

Mail going overseas has the following suggested deadlines:

Global airmail parcel post should be sent by Dec. 6 to Africa, Central and South America; Dec. 10 for Europe; and Dec. 13 elsewhere.

For airmail cards and letters the suggested deadlines are Dec. 6 for Africa, Central and South America and Dec. 13 for the rest of the world.

Global express mail should be sent by Dec. 11 to Africa, Central and South America and Europe; Dec. 17 to Asia, the Pacific, Australia, New Zealand, the Caribbean, Mexico and the Middle East; and Dec. 18 to Canada.

Global express guaranteed items can wait until Dec. 21 for Canada and Dec. 20 elsewhere.