With estimates suggesting that as much as 84 percent of all e-mail is spam, it's a good idea to approach every message with suspicion. Experts recommend that home Internet users choose an Internet service provider that provides spam protection, and to make sure that they're running updated anti-virus software. But even with those precautions, some unwanted messages will seep through. Here are a few things to keep in mind when you're deciding whether to open that message.

* Beware of Your Bank: This may sound counterintuitive, but you should be immediately suspicious of any e-mail message from a financial institution, especially if it asks you to submit or update your personal information. Even though some of these e-mails look legit -- a new one purporting to be from Citibank uses the official Citibank logo, for instance -- such messages are often the vanguard of "phishing" scams designed to bilk you out of your sensitive financial data. If you have any doubt, call your bank directly or enter its Internet address into a separate browser window. Under no circumstance should you click on the links in those messages.

* Don't Talk to Strangers: The advice you give your kids as they strike out into the world is a good axiom for you to follow online. When in doubt, don't open e-mail from people or organizations you don't know. Be particularly leery of e-mail coming from nonsensical alphanumeric addresses, like qdg199997@yahoo.com, which are often created automatically by "bots" used by spammers to automate the process of deluging your inbox. If it looks fishy, delete first and ask questions later.

* Steer Clear of Attachments: The rule of thumb on attachments is: Unless you're expecting it, don't open it, even if it appears to be from someone you know. Many Internet viruses spread themselves by invading the e-mail systems of infected computers and sending copies of themselves to the compromised machine's entire address book. That unexpected attachment from your mom could be a virus. When in doubt, call the sender and ask if he or she sent the message.

* Check the Spelling: One of the cruder tactics used by spammers is to deliberately misspell words so that they're not snagged by spam filters. It may seem obvious, but you definitely shouldn't trust any e-mail offering V1agr.a or Z000loft. Then again, you probably want to avoid the ones selling Viagra and Zoloft, too.

* Watch Those Non Sequiturs: If you do open a message that says "BBQ This Weekend" and the body of the message is a description of a penny stock, you probably have a spam message on your hands. Spammers often use innocuous, generalized subject headings to prompt users to open their messages.

-- David McGuire