If you've ever posted your email address online or given it to the wrong company, you know how rampant unsolicited emails are. They come in droves, promoting pharmaceuticals, penny stocks, and adult websites, and phishing for sensitive information. And if you have been seeking home business opportunities, you've probably gotten your fair share of business scam emails, too.

Some of these scam emails look very legitimate, and it can be hard to tell whether or not they are for real. Here are some of the more common types of email scams.

* Payment processing jobs - Scammers often send out emails offering jobs processing payments. They claim that you can make money by receiving and cashing checks, then wiring the money (minus your fee) to the end recipient. But in most cases, the check is bogus. The bank doesn't realize this until the check has cleared, which can take a couple of weeks. So they then debit your account for the amount of the check, and the scammer walks away with the proceeds.

* Medical billing jobs - Doing medical billing from home sounds legitimate enough, especially when a company promises you training, software, and job placement. But when you send them your money (usually several hundred dollars), you often get trained to use out-of-date software, and then receive a list of doctor's offices in your area to call and see if they will hire someone to work from home. In reality, most offices prefer to have their staff on-site, especially when they start.

* Email chain letters - This is a new twist on a very old scam. You receive an email asking you to send money to the other people on the list, usually through PayPal. Then you are supposed to forward the email on to a certain number of people after replacing one of the names on the list with your own. In theory this could work, but most people who receive the email do not participate. And more importantly, this type of activity can cause your PayPal account (and possibly your email account) to be shut down. When circulated through the postal system, these types of letters are illegal.

* Business opportunity scams - There are many types of business opportunity scams that can be promoted via email. Some are fronts for pyramid schemes, which involve earning commissions by recruiting other people into the program, not by selling actual products. Others offer information about how to make money online in various ways for a fee, then they don't deliver. And some offer direct sales type opportunities, but collect money from reps without delivering the products.

When you're trying to get started making money online, wading through the scams can be tricky. If you are in doubt about a particular opportunity or job offer, do some research on the company. Try to contact them, and if you get someone, ask lots of questions. If you are unable to get in touch with anyone after a few attempts, chances are they have something to hide. This may sound like a lot of extra work, but it's worth it to stay away from the scams.