I own a few domain names, which means that I have the ability to create an unlimited number of email addresses. This is a cheap and effective way to reduce email spam in your inbox.
Whenever I purchase something from a web retailer that I've never used before, I create a custom email address that includes the name of the retailer. I do the same when I register for shareware and especially when I register at an online forum.
For example, if I plan to buy something from somewebstore.com, I create an email address call somewebstore@EXAMPLEofoneofmydomains.com, and I use that address exclusively for that web store. If start to receive spam to that address, I simply disable the address, and the spam stops.
Recently, I had to disable two addresses, one I used to register software called Shinkuro and one I used for a forum to discuss the KMPlayer media player software.
KMPlayer is an interesting media player for Windows, as it is mish-mash of features taken (stolen?) straight from other media players such as WinAmp, as well as various open source projects. I assumed that the Korean-based forums were insecure, and I was right. Within 3 weeks, I noticed that my custom kmp@EXAMPLEofoneofmydomains.com email address was being used as a Reply-To for someone sending spams. And I never even posted a message to the forum.
Shinkuro was surprising, as they are a company that creates collaboration software for government use, and is partially funded by DARPA . I created a custom shinkuro@EXAMPLEofoneofmydomains.com address to try the software, and never used it for another purpose. But this year, I started getting Nigerian 419 scams sent directly to that address. Would you trust the security of Shinkuro now?