Every day, businesses mail credit cards, applications, invoices and promotional literature to their credit card customers, trusting the mail to be a safe way of doing business. But the mail is not safe, no matter how hard U.S. postal inspectors try to protect us.

Criminals and opportunists find the theft and fraudulent use of credit cards to be an increasingly convenient means of illegally obtaining cash, drugs, services and merchandise. But the villains here are not hardened street criminals; they are most often cashiers, retail clerks, bellhops, maids and other employees.

Airline cargo handlers, couriers for banks, mail presort employees, postal clerks, mail sorters, postal carriers, credit card company employees and contractors handling mail as undeliverable – are all in occupations providing access to large volumes of mail. People in these occupations are increasingly being implicated in credit card thievery.

But these part-time blue collar criminals pale by comparison with the activities of street gangs and sophisticated financial criminals who have created an unparalleled demand for “plastic.” And these crooks find the U.S. mail to be a fat target.

Postal robberies and thefts from postal vehicles, depositories, receptacles and mail storage boxes have increased during recent years.

To protect yourself, you first need to understand how crooks get to your credit cards by accessing your mail. Here’s how that happens:

. By obtaining your account numbers from stolen credit card statements and using the information to order merchandise by telephone or to obtain duplicate or additional cards at a different address by saying that they have lost their card or changed their address, or wish another person to be issued a card on the same account number.

. By stealing checks endorsed payable to credit card companies and increasing their own credit lines – then taking cash advances.

. By filing false change of address orders to divert mail so they may obtain your account information.

. By stealing preapproved credit card applications and submitting them after changing the mailing address and the application.

. By collusion between mail thieves and unscrupulous business owners.

Credit card issuers are devising ways to discourage thefts and reduce financial losses, which credit card companies then pass on to consumers. But the bottom line is that it’s up to you to protect yourself.

U.S. postal inspectors suggest the following:

. Use plain envelopes so credit-related mailings, statements, and payments are less obvious.

. Consider varying the appearances and-or color of envelopes you use.

. Support industrywide procedures to circumvent unauthorized use.

. Mark envelopes “Do Not Forward” to reduce receipt by unauthorized persons.

. View with concern marketing and operational practices that permit applications and address changes by telephone. These practices have an obvious potential for fraud and theft.

. Be skeptical of third-party checks used for credit card payments.

. Watch your monthly statements closely for unusual or unauthorized activity. Call your credit card company and check if you have questions. If you suspect mail theft or fraud, report it to your local postal inspector. When you receive unsolicited offers of credit, cash advances or equity loans, rip them into shreds before placing them in the trash. Crooks love your trash.

. And if you work in one of the occupations mentioned above and have legitimate concerns that a fellow employee is perpetrating mail theft, report it to a supervisor. We are all brought up not to “snitch,” but that’s why they get away with it – because no one speaks out.

Consumer Forum is a collaborative effort of the Bangor Daily News and Northeast COMBAT. Send questions to Consumer Forum, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. COMBAT is a nonprofit organization with annual dues of $10. For membership information, write to the above address.