Long Island business owners who went out of their way to pay bills the safe way, or so they thought, issued a warning on Tuesday.

Their mail got stolen anyway.

It's all part of a crime called check washing, and experts say it's very difficult to prevent.

"This is an everyday occurrence. It's constantly happening"

Like many, father and son Rich and Dan Miller, who are in the trucking business, take a detour to mail checks at the Bay Shore Post Office.

"I mail it in front of the post office because I feel like it's the safest place. I figured it would be on camera," Dan Miller said.

Yet they say someone fished their checks out of the blue box, even after the U.S. Postal Service ramped up security, making slots harder to access.

"I went to the post office to file a complaint and they said this is an everyday occurrence. It's constantly happening," Rich Miller said.

Check washing is the low-tech crime of washing off the ink and rewriting the check. The Millers' checks were cashed in Brooklyn for nearly $3,000.

"I see 'Derrick Johnson' on there, the amount is changed and everything, totally different handwriting," Dan Miller said.

"We had to close all our accounts. We had to open accounts. We are still trying to figure out who got paid, who didn't get paid. It is a nightmare," Rich Miller said.

"Trying to get fees waived because mortgage payment wasn't paid, health insurance wasn't paid," Dan Miller added.

How to protect yourself

A rash of mail theft nationwide for years prompted the USPS to roll out high-security collection boxes that make mail fishing, which is often done with glue traps, more difficult. However, one veteran postal carrier, who reached out to the Millers with advice, told them it's hard to stop.

"They've done it in front of Carle Place Post Office, Huntington. It's going on all over," the postal carrier said.

His advice is for people to use a gel pen, because "they cannot be washed."

However, criminals have evolved. Checks can also be digitally duplicated and printed.

Experts say your best defense is to pay electronically or go into the post office and hand it to the clerk.

"I want everyone to know about it, especially the elderly. You know, these people don't pay online," Rich Miller said.

Some post offices are equipped with outdoor surveillance cameras, but not the century-old building in Bay Shore. A federal bill to pay for cameras at all post offices failed to pass in Congress.