Tame the E-mail Tangle
First, we all probably remember the phrase "Garbage In, Garbage Out." Whenever an online form solicits my e-mail address I first evaluate whether I truly want to receive e-mail from this company. Perhaps I'm only browsing anonymously for interest rates, etc. I may purposefully choose to give a bogus address if the site requires something in that field.
On the collecting end, several inexpensive options are available to test the validity of received e-mail information. The expensive route is to attempt to verify the address by overlaying the received data with one of the major information houses. While often a good approach, particularly when you're looking to obtain additional information about this customer (e.g., demographics), the cost of this type of append usually is not reasonable for your first line of prospecting.
A quick and dirty approach to validation is to test the existence of the domain name that has been supplied by the customer. Someone with basic programming skills can write simple scripts to loop through a list of domain names and determine if they're valid simply by pinging the domain (sending a special message to the host in hopes of receiving a reply). If a positive reply is received, you at least know the domain exists, though the exact e-mail address has not yet been validated.
Identifying the Right Address for the Objective
The next three steps follow the traditional marketing mantra of recency, frequency and monetary value to determine which e-mail address—out of multiple possibilities—might be the best for a particular customer.
Recency. How long ago was this e-mail address supplied? Since e-mail addresses can be short-lived, you may want to place emphasis on addresses that have been entered more recently. Simply keeping a field called "date acquired" in your e-mail address data table can greatly improve your ability to reach the best address.