One old saw about newfangled email is that it's as private as a postcard. Problem is, many people feel it's as secure as a Registered Mail letter.

Two recent events shed interesting, and useful, light on the issues surrounding email security.

A new study by Forrester Research, commissioned by email security provider Proofpoint (www.proofpoint.com), found that 41% of companies with 20,000 or more workers pay employees to manually read or automatically analyze the emails sent by other employees.

These companies are looking for instances of confidential data being leaked, either purposely or inadvertently, to those outside the company. Such snooping is perfectly legal, with U.S. courts ruling that emails sent or received using company equipment are company property and are therefore rightfully accessible by management.

You can be fired for revealing too much in email, instant messaging, and texting as well as for posting unauthorized information in blogs, internet discussion groups, social networking sites such as MySpace, and media-sharing sites such as YouTube. According to the Forrester study, 26% of large companies indicated they had fired at least one employee for violating its email policy.

Another common fallacy is that if you want to avoid potential problems down the road with email, delete the message after sending or reading it and ask your correspondent to do so as well.

The fact is that even if it's not immediately intercepted, an email may be read by others later. Email endures. As with files on your hard drive, when you delete an email message, it's not really gone. It can be retrieved, among other ways, from tape backups months or even years later.

On the other hand, don't think that because management has the right to read your email, you have the right to read the email of management or other employees.

In one recent high-profile case still playing itself out, the FBI is investigating a Philadelphia TV news anchor for allegedly reading the email of a former co-anchor.

The FBI raided the home of Larry Mendte of KYW-TV, seizing his computer after a fellow employee had discovered that he may have signed on to Alycia Lane's Yahoo! email account at work and read her email (if he did, it's not clear how he got her password).

Lane had been fired by KYW 6 weeks earlier after several "embarrassing" events, such as allegedly striking a police officer and emailing photos of herself in a bikini to a married man. The authorities were trying to determine if Mendte used Lane's emails to leak information about her to gossip columnists.

It's a federal crime to pry into another person's email in this way.

In general, it pays to be smart about email. This applies to employers too, large as well as small. One frequently repeated piece of advice is to create a company email policy that explicitly spells out appropriate, and inappropriate, uses of email and management's legal right to it. This will help prevent problems in the first place.

Companies may also be required to retain old email. According to new corporate reform legislation, public companies that deliberately delete email with the intention of obstructing a federal investigation can face a fine of up to $1 million.

A number of programs can help with both archiving and analyzing company email. MailMeter Archive from Waterford Technologies (www.mailmeter.com), for instance, is used by companies having from five to 5,000 employees.

The program captures all email that employees send or receive and archives messages in a database. It also lets you analyze email to detect patterns. This can help you determine who's sending too many email messages or too few, who's emailing an important client, or who might be using email inappropriately for sending jokes, music, porn, or your customer list.

If you need to ensure that email isn't seen by eyes other than those you intend, one option is to use an email encryption program. For some time now the standard has been Pretty Good Privacy, now called PGP Desktop (www.pgp.com).

The program automatically encrypts email and lets you send "self-decrypting" messages to those who don't have the program. It's available to try out for free for 30 days.

Email has great utility, whether for business or home use. But it's no panacea. Like any communications medium, it has its strengths and weaknesses. Sometimes it makes more sense to pick up the phone, mail a letter, use an overnight delivery service, or stop by the cubicle of a co-worker to chitchat in person.