The recent theft of mail from a mailbox outside a Post Office in California highlights the generally unconsidered risk of identity theft presented by merely mailing a bill with a check by way of a letter dropped off in a mailbox. Identity thieves will steal mail with checks in them and can then use simple software programs to make forged checks that can be used to empty your account. They also can steal your credit card bills and change the address of your account and have the account sent to them. Since they will also have access to your credit card number and name from the bill, they can use this information to use your credit card, sometimes for a matter of months before you discover that your credit card has been illegally accessed.
As soon as you find out that your account has been illegally accessed, notify your bank to have the illegal charges removed. You also should consider paying your bills online. It is safer than paying through the mail. When you do mail checks or bills, drop them off directly inside the post office.