Internet addresses change much more rapidly than physical addresses. While less than 5% of all physical addresses change annually, industry experts estimate that over 25% of all email addresses change annually.¹

That means that email directories are highly inaccurate. Nonetheless, I can recommend these useful sites:

- addresses.com - bigfoot.com - searchbug.com - intelius.com ($)

If a person has changed their email address, they may have registered their new email address with a change of address service such as emailchange.com.

If you are looking for a person's email address, and none of the directories list him or her, there are a few things you could try.

• Search their name using Google Groups - perhaps they've posted to a newsgroup.

• Guess their email address from their company's URL. For example, if you knew that Fred Flintstone worked for a company with the website www.sladequarry.com, you might try: fflintstone@sladequarry.com.

• Guess their email address from the URL of their ISP. I once had a case where subject of the file (lets call him John Doe) lived in a small town in northern British Columbia. I determined that there were only two ISPs who served the community: net.com and speed.com (just examples). I tried jdoe@net.com and jdoe@speed.com, then waited for a reply. To find out which ISPs service a particular community, you could check the Yellow Pages or search the List of ISPs.

Try yellowpipe.com (Firefox only) or Email Verifier (click on SMTP Verify) to validate an email address.

Email directories are notoriously bad, so their reverse lookups aren't going to be any better. Still, you could try intelius.com.

If you are viewing a posting that someone has made to Google Groups you can see other postings they have made - just click on View Profile.

Corporations often use the same structure for the email addresses of all their employees. If John Parker's addresses is jparker@abccompany.com then you can guess that Sally Smith's email address will probably be ssmith@abccompany.com.