The U.S. Postal Inspection Service (USPIS) is reminding the public that they should be careful when mailing cards and gifts over the holiday season.

Americans should be wary of the times they put important mail into blue U.S. Postal Service (USPS) collection mailboxes, according to the law enforcement arm of the national mail service.

"Deposit outgoing mail into blue collection boxes before the final pickup of the same day of deposit," a spokesperson for the USPIS told Fox News Digital. 

WHY PEOPLE ARE FINDING DRYER SHEETS IN THEIR MAILBOXES

"Check the pickup schedule posted on the box to ensure your mail will not sit in the box overnight or over the weekend; and use the letter slots inside your Post Office for your mail, or hand it to a letter carrier," the agency’s statement continued.

Mail dropbox in Philadelphia being targeted by thieves

In September 2022, authorities say a mail dropbox outside a Pennsylvania post office has been struck dozens of times by thieves searching for money and checks.  (FOX 29 Philadelphia)

The USPIS noted that the federal mail system is one of the "safest and most trusted ways" to send gifts and greeting cards to family and friends.

The agency also told Fox News Digital that it encourages all customers to follow mail theft prevention tips offered by the USPIS to safeguard mailed letters and gifts.

The USPS reportedly delivers mail to more than 100 million addresses, according to the USPIS. 

USPS ADDS 'VIRGIN AND CHILD' PAINTING TO NEW FOREVER STAMP BEFORE CHRISTMAS 

A local Postal Inspection Service office wrote in a recent press announcement that criminals tend to target collection mailboxes "after the last collection of the day or during Sundays and federal holidays."

"If customers simply used retail service or inside wall drop slots to send their U.S. Mail, instead of depositing it to sit outside overnight or through the weekend, blue collection boxes would not be as enticing after business hours to mail thieves for identity theft and check-washing schemes," the local mail inspection office wrote.

A view shows U.S. postal service mail boxes at a post office in Encinitas, California February 6, 2013. The Postal Service plans to drop Saturday delivery of first-class mail by August in its latest effort to cut costs after losing nearly $16 billion last fiscal year, the cash-strapped mail agency said on Wednesday. REUTERS/Mike Blake (UNITED STATES - Tags: BUSINESS EMPLOYMENT POLITICS) - RTR3DF9F

The U.S. Postal Service's blue collection boxes are open to the public. USPS customers drop mail and packages into the boxes for delivery by authorized USPS personnel. (REUTERS/Mike Blake)

In a "Neighborhood Watch: Protect Your Mail!" flyer issued by the USPIS, Americans who feel they can’t trust the collection mailbox in the area they live in are advised to place mail in a collection mailbox in another area or use a secure mail receptacle at their place of business.

Suspicious activity, mail or identity theft, fraud, and seemingly tampered mailboxes that have glue, tape or a sticky substance attached should be reported to the USPIS, the agency’s flyer says.

USPS ADDS 'VIRGINA AND CHILD' PAINTING TO NEW FOREVER STAMP BEFORE CHRISTMAS

The USPIS can be contacted by phone through its national hotline at 877-876-2455.

Other mail theft prevention tips the USPIS offers customers include picking up mail promptly and not letting it sit in mailboxes overnight and contacting issuing agencies right away if important or valuable aren’t received as expected, such as checks, credit cards or negotiable items. 

Mail in hand in front of open mailbox

The U.S. Postal Inspection Service urges people to not leave mail or packages in mailboxes overnight because there is a risk of mail theft, which could lead to identity theft, fraud and financial loss. (iStock)

The USPIS says customers should notify the postal service if they change their address or are going away on a trip and need their mail held at a facility until they return. 

The agency also advises against mailing cash.

USPS customers have the option to sign up for the postal service’s Informed Delivery notification service, which sends daily email notifications of incoming mail and packages.

CLICK HERE TO GET THE FOX NEWS APP

The USPIS reportedly investigates and arrests thousands of mail thieves each year, according to a "Mail & Package Theft" page on the agency’s website.