Free anti-spam protection for your email address. Redirection links, disposable aliases.

Spammers use all the available hardware, software and techniques to collect as many email addresses as possible.

Spammers' methods

A few words on how spammers build their databases. If you'd like to read about their methods of sending SPAM - check the Links section.

Robots
The software utilized by spammers to collect email addresses (the robot) is called a "harvester". It's job is quite similar to search engine crawlers - it visits a website, scans its contents and then follows all the links it finds on the pages. The only difference is that a harvester saves only email addresses. It can find email addresses both - in the text displayed and in the "mailto:" link.

Sites
One of harvesters' favorite places are forums and newsgroups (usenet). They can even register as fake users to obtain full access to all the posts.
Very often they run their own websites offering some simple features (files download, online games, etc.) but only to registered users. In this case - in fact - it is not SPAM, because by registering users agree to website terms & conditions (ususally without reading them). And the website owner has full rights to use the addresses - which often includes sharing the database with third parties.
Conclusion: your own website/blog is not the only place when spammers could find your email address.

Viruses
Harvesters are not the only tools spammers use to obtain email addresses. They also use viruses and trojan horses. These little ugly programs reside in computer's memory and scan user's address books and email messages. This is the reason why you shouldn't send group messages by putting all of your friends in "TO" or "CC" field. If only one of your recipients computers is infected, all of their email addresses will appear in spammer's database. Try using "BCC" field instead - or some email marketing software.

Verification
Spammers' databases are huge - they consist of millions of email addresses. Their servers and botnets (networks of zombie-computers that spammers have taken control of) would finally stuck if they don't verify the databases and remove inactive addresses.
They obviously remove email addresses that no longer exist - because messages are bounced.
But they also remove addresses of users that don't read their mail for a long time. How do they check if the message is read? They send HTML messages including a little code that loads invisible content from their server. It is strongly suggested to turn on the option of displaying HTML messages by default in your email client.

What do do?
A few simple suggestions:

think twice anytime you'd like to type in your email address
use spamstone image generating option to publish your email address as a GIF file instead of open text
use spamstone http redirection link instead of "mailto:" link with your address
use spamstone aliases for every untrusted registration
when sending a group message, don't put your friend addresses in "TO" nor "CC" field, try "BCC" instead
turn the default HTML message display option off in your email client.