Many times, mail theft is a crime that goes unnoticed and unreported and that makes it nearly impossible to gauge the total impact. But, some estimate that it's a billion dollar a year business in Colorado alone, with criminals in many cases cashing in on everyone's mistakes.

One mail thief who talked to 7NEWS Investigator Tony Kovaleski asked not to be identified and wanted his face disguised.

"You're talking maybe 30 seconds with a screwdriver or a dent puller. You drill in the dent puller, you pop it out. You can open 10 of them in about six minutes," said the former mail thief, identified as "Matt."

For two years, Matt stole checks, credit cards and identities from Colorado mailboxes. He claims his group regularly generated large amounts of cash.

"We're looking at $2 million. That's quite a good income for people who are not college educated," he said.

His scheme started at a neighborhood mailbox.

During the past three years in Colorado alone, there were 803 reported mailbox break-ins.

"For me, it didn't get any easier or any more lucrative," Matt said.

Experts told 7NEWS that the problem is probably much greater because, many times, the crime has no trail. The victims are sometimes unaware and the criminals go unchecked.

"I had people who worked inside the postal department who brought me mail," Matt said.

A surveillance camera video obtained by 7NEWS shows how thieves can open and unload dozens of mailboxes in a matter of minutes.

"I think about the people who had their lives savings in those checking accounts and I drained their checking accounts. And I feel bad about it now," Matt said.

7NEWS' analysis of reported break-ins during the past three years showed that thieves are most attracted to neighborhood cluster boxes and apartment panels. In fact, those two types of mail receptacles make up nearly 90 percent of all break-ins.

"We know that it's a significant problem," said Denver District Attorney Bill Ritter, who has prosecuted dozens of mailbox thieves. "They will limit it to a geographical area because they can work it a lot quicker."

7NEWS found three metro areas hard hit by mailbox thieves.

A zip code cluster in Arvada experienced 59 break-ins in the past three years. A cluster in Thornton, Westminster and Broomfield had 100 mailbox crimes and another cluster in Lakewood and Golden experienced 128 mailbox break-ins in the same period.

"They are basically the pot of gold at the end of the rainbow for somebody who may be under the influence of drugs," said Matt.

Matt admits methamphetamine was part of his driving force and law enforcement agents say it's not uncommon for a large trash bag of mail to be discovered during a meth bust.

"Everybody who does mail fraud -- I would say 99 percent of them -- are meth users, manufacturers or distributors of some sort," Matt said.

Three years ago Matt's run of drugs, cash and crime ended. He spent a year behind bars and will spend the rest of his life repaying his debts to society.

"The day I felt most accomplished was the day I turned myself into jail and was done with it all," Matt said. "I finally decided I'd had enough of it about the fifth time I had been arrested, went to jail and my world was turned upside down. I was done with it and didn't have to look over my back anymore."

The seven Colorado zip codes with the most mail thefts in the past three years is 80127 in Littleton, 80110 in Englewood, 80227 in Arvada, 80226 in Lakewood and Denver and 80401 in Golden. The top on the list was 80031 in Westminster. That area led the state with 34 break-ins in the past three years.

Where does your zip code rank with the criminals? Check out our list.

If you want to make things difficult for mailbox thieves, the postal inspector said pick up your mail everyday, deposit outgoing mail in U.S. Postal Service collection boxes, shred unwanted documents that contain your personal information and review your consumer credit report annually.