Postal authorities and local police are alerting residents of Dorchester and Mattapan that they should be careful when using the United States Postal Service’s blue mailboxes, citing an increase in mail theft around the neighborhood and regionally, especially during certain time periods. The warning is addressed in particular to bills or payments that include a check.

“An ounce of prevention in this is worth so much,” said Danielle Schrage, postal inspector at the US Postal Inspection Service’s Boston branch. “We don’t want people to be afraid of mailing. We think mail is incredibly safe. We carry millions of pounds safely every day, but these criminals target boxes at certain times.

“Please, please do not let your mail sit in the boxes, particularly overnight, on weekends, or on federal holidays,” she added. “That’s when these boxes are targeted for theft, usually in the dead of night. Bad guys know when stuff sits, and we want to make sure we don’t leave it there for them.”

In that regard, several local organizations and residents have learned lessons that the hard way, particularly when it comes to thieves stealing payments and “washing” checks, a process by which criminals will obtain checks unlawfully, often by fishing correspondence out of mailboxes, and wash them in chemicals to remove the ink and change information such as the payee’s name and/or the dollar amounts. The offenders will then deposit the fraudulent check into a bank account under their control.

Unfortunately, in many instances, the victim or bank doesn’t discover the checks are counterfeit until weeks or months later.

Annie Le, of the Boston Little Saigon organization, noted at the Fields Corner Civic Association meeting this month that they had three payments stolen from them and suspected they came out of a mailbox in the neighborhood. One was altered and cashed, and the other two were flagged by the bank and not cashed.

During the meeting, C-11’s Sgt. Tim Golden said this kind of crime is happening all over the city, and he told residents that “it’s a good idea right now to go inside the post office and mail letters.”

Schrage agreed with Golden, but again said mailboxes can still be used safely, provided one uses a little strategy. Find out when the pick-up time is for the box – that information is typically attached to the box – and drop your mail into it shortly before the pick-up

Mail theft is not a new crime, and postal inspectors have been investigating it successfully for many years, said Schrage. In fiscal year 2021, postal inspectors made1,511 arrests for mail theft, and worked with local, state, and federal authorities to obtain convictions of 1,263 thieves. Some of the tools the inspection service uses to address the crime of mail theft include investigative, technological, and prevention tactics.

Instances of mail theft should promptly be reported to the US Postal Inspection Service and/or the local police department. Schrage advised residents to report mail theft to her office first, as a local police report may not get to them. A report can be filed online at uspis.gov/report or by calling 1-877-876-2455.