CHICAGO (CBS) – If you’re heading out to the post office today to mail your Christmas cards, expect some big lines; the U.S. Postal Service expects Monday to be the busiest mailing day of the year, with more than 1.7 million cards mailed in Chicago alone.

WBBM Newsradio’s Regine Schlesinger talked with customers at the post office at the Aon Center downtown, where the line started forming as soon as the post office opened its doors at 7:30 a.m.

One woman said she normally sends her holiday mail earlier.

“I just put it off, that’s all,” she said. “One box going to a military person in Spain.”

She said she expected long lines, so she got to the post office early, rather than waiting for her lunch break, when she figured the wait would be even worse.

LISTEN: WBBM Newsradio’s Regine Schlesinger reports

With the post office in deep financial trouble, some people worry about its survival.

Dale Griffin was mailing holiday packages. He said with all the Postal Service’s financial troubles, he’s worried about its future.

“I’m one of the holdouts for snail mail. I think there’s a lot of charm for something physical that you receive, rather than an email. So I make cards and send them,” he said.

Gilbert, who was doing his holiday mailing, said, “not worried, but I hope they solve their problems.”

He said he still uses the post office a lot. Another person was in line to buy stamps for all the “Thank You” notes she’s written for wedding gifts. With that taking up so much of her time this year, she’s skipping the Christmas cards.

The Postal Service estimated 97 million customers will come to the post office this holiday season and more than 47 million will do online shipping from home.