To protect your mailbox from undesirable correspondence, do not publish your e-mail address on Internet forums and switch on the server-side spam filter provided by the SpamAssassin software. Also ask your provider to switch on protection from spam and phishing based on DomainKeys.
DomainKeys is based on sender authentication. When an e-mail claims to originate from a certain domain, DomainKeys provides a mechanism by which the recipient system can credibly determine that the e-mail did in fact originate from a person or system authorized to send e-mail for that domain. If the sender verification fails, the recipient system discards such e-mail messages. Verification of incoming mail can be switched on only by your provider; however, you can switch on signing of e-mail messages that are sent from your domain: Home > domain name > Mail > Preferences > Use DomainKeys spam protection system to sign outgoing e-mail messages option.
When you need to publish your e-mail address, you may want to create a disposable e-mail address - e-mail alias - for your primary e-mail address, and publish it instead. All messages sent to the e-mail alias will come into your mailbox. Once you start getting spam, remove that alias and create another one. If you have a mailbox at another domain or mail server, you may want to set up a disposable e-mail forwarder.