How often have you heard this?  Perhaps even thought it?  I know I’ve been asked about it more often than I can count and see it crop up on every web board I frequent at some point in time.  The story is always the same…

I signed up for a Hotmail account, never told anyone about the address, only used it a couple times to e-mail friends and within a couple days I was already getting junk e-mail!  Microsoft must have sold my e-mail address to spammers!  How else could you explain them sending me spam when I didn’t tell anyone my new address?

Well, I can tell you with absolute certainty that Microsoft did not sell your e-mail address to anyone.  Junk e-mail is actually so costly to Hotmail that if we were to try to make a business out of selling e-mail addresses to spammers the addresses would be so expensive that spammers couldn’t afford them. 

But if Microsoft didn’t sell my address, and I didn’t tell anyone my address, how did the spammer know to send me junk mail?

The answer is simply: they guessed.  Spammers invest a lot of time in generating software designed to be good at generating possible e-mail addresses.  The software performs what’s called a “dictionary attack” by taking a list of words and names and combines them into every conceivable address.  The word list can include e-mail addresses found in public locations (e.g. if xxx@test.com posted to a newsgroup you can bet that xxx@hotmail.com will get spam).  After constructing their list the spammers then try to send e-mail to their list of constructed e-mail addresses.  In order to increase their odds, the spammers will identify the largest ISPs to test out their new e-mail lists.  As the world’s largest free e-mail provider (source: Guinness) it’s no wonder spammers hit us hard.  After preening their lists the spammers then change the domain names and start hitting other sites.

Junk E-mail costs Hotmail a lot of money.  In, fact, junk e-mail costs everyone money (estimated cost to businesses last year: $10 billion).  Businesses hate it, consumers hate it, ISPs hate it.  There is no possible way for Hotmail to profit by selling your address, the cost in customer support complaints alone would be enough to sink us.  Add the storage, administration, networking, PR and legal costs to the pile and there isn’t a spammer out there who would be able to afford to buy our list were it for sale.

In short, no, Hotmail didn’t sell your e-mail address.