You're losing E-mails. It's almost certain that some significant percentage of your legitimate outbound E-mails aren't getting to their destinations; or that some significant percentage of your legitimate inbound E-mails are being lost before you ever see them.

When I say "significant," I don't mean a few. I mean something like 40%, or even more in some cases. And I'm not talking about losing junk mail. I'm talking about the loss of totally valid, non-spam/non-junk E-mail.

Think about that for a minute: As many as four out of 10 of your serious E-mails--the sort you might exchange with co-workers, friends, business associates, or customers--may not be making it to their intended destinations.

This alarming statistic is derived from a large test I conducted late last year, involving more than 10,000 participants. I announced the test with a call for volunteers in an issue of my E-mail newsletter last October. It said, in part:

...I'd like to gather a group of volunteers... and send each one a simple non-spam E-mail message, in plain text and with no attachments, from a personal mail account (not a bulk mailer). I'd like to see how many of these simple messages actually make it through the gauntlet of servers, routers, and ISP-based and local mail filters.

I won't tell the volunteers in advance what address the mail will come from or what the subject line will be.... Rather, I propose to simulate a normal, unanticipated, plain text, non-spam E-mail, as if between friends or coworkers, and see what gets through....

I included specific sign-up information, and asked interested readers to indicate their willingness to participate by sending a reply E-mail to a designated mailbox.

I'd hoped for maybe 500 volunteers. But less than a day after my request went out, I was astonished to see that more than 10,000 people had signed up. Clearly, E-mail reliability is a real hot button!

To keep the size of the test manageable, I then stopped accepting additional applications to participate, ending up with 10,979 volunteers on tap.

It's important to note that these test participants were eager, motivated, and E-mail savvy: They had learned of the test via E-mail, and had signed up by E-mail within hours of the call for volunteers going out. Thus, if anything, this body of E-mail-enthusiastic volunteers represents a best case for E-mail success, a fact that puts the dismal test results in an even starker light.