Anytime that e-mail is used, it makes its way over many different servers before it arrives at its destination.  The e-mail address in question can be "collected" at any of those points along the way.  Not to mention that the content of the e-mail itself can be read by who-knows-who.

I've heard it said that e-mail is a postcard.  And the address on the card is not hidden from anyone who bothers to look at it.

Encryption might help to keep the contents of an e-mail private.  But I know of no way to encrypt an e-mail's address -- outside of spoofing an account or else zombifiying other machines.  In which case the e-mail address hasn't been encrypted -- it's just been stolen.

Something To Do At 3:00AM