A lady emailed me yesterday very upset over the fact that her friend's Internet Service Provider (ISP) wasn't delivering important email messages.

This lack of delivery caused a real problem for the two of them with ruined plans, missed appointments, and just plain inconvenience.

If you don't use email, this might not sounds like a "big deal."

But this problem of non-delivery has dramatically affected the way businesses use email and is now about to reach epidemic proportions for consumers using email.

To put things into perspective, imagine if every time you dialed a friend's phone number you had no idea whether it would ring or not.

Now imagine how frustrated you would feel over time if you kept dialing the same number and it never rang for you, but others could get through and your friend's phone number never changed.

That's exactly how you'll feel when your personal emails start getting blocked for seemingly no reason.

The problem of legitimate email messages not getting through stems from the uncontrolled and unstoppable onslaught of spam that currently grips the Internet with seemingly no end in sight.

The fact that viruses can now "spoof" email addresses and make it look like someone sent a virus to thousands of people doesn't help matters either.

In an effort to cut down on spam, ISP's implement a number of counter-measures, including: text filters, spam databases, and IP blocking.

If your email message doesn't get delivered, most of the time it means you inadvertently got caught in an ISP's "defense system."

If you ever find your email messages don't get through, or if you'd like to head off problems before they occur, the following tips should help.

Encourage all your email contacts to "whitelist" your email address in their email program.

Just like you can say which email addresses you don't want to get messages from, you can specify a list of email addresses you always want accept.

In Yahoo or Hotmail you can set up your filters to accept email messages from a certain source regardless of the subject line or content of the message.

It takes a little patience to set up, but it pays big dividends by not losing important messages.

With Outlook and Outlook Express, you can set up message rules to always accept messages from certain senders.

If you send messages to people who use AOL, try this technique. Get them to add you to their address book "safelist" or "approved senders."

This helps AOL identify that the message recipient "knows" you and has a higher likelihood of actually wanting to receive your message.

Email AOL tech support for help on this if you encounter a problem.

If filtering and "white" listing don't work, then your friend needs to contact their ISP to sort out the problem.

Their ISP can certainly figure out why messages don't get through, but it may take some concerted encouragement to get the ISP's customer service to take the time to investigate the cause.