To protect your mailbox from undesirable correspondence, do not publish your e-mail address on Internet forums and switch on the server-side spam filter provided by the SpamAssassin software.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, if server policy allows, you can switch on signing of e-mail messages that are sent from your domain: Domains > domain name > Mail group title menu > Mail Settings > Use DomainKeys spam protection system to sign outgoing e-mail messages option.
If you use a Linux-based hosting account, then you can also use the spam protection based on greylisting. Greylisting is a spam protection system which works as follows: For every e-mail message that comes to the server, sender's and receiver's e-mail addresses are recorded in a database. When a message comes for the first time, its sender and receiver addresses are not listed in the database yet, and the server temporarily rejects the message with an SMTP error code. If the mail is legitimate and the sending server is properly configured, it will try sending e-mail again and the message will be accepted. If the message is sent by a spammer, then mail sending will not be retried: spammers usually send mail in bulk to thousands of recipients and do not bother with resending.
The greylisting protection system also takes into account the server-wide and per-user black and white lists of e-mail senders: e-mail from the white-listed senders is accepted without passing through the greylisting check, and mail from the black-listed senders is always rejected.
When the greylisting support components are installed on the server, then greylisting is automatically switched on for all domains. You can switch off and on greylisting protection for individual domains through Parallels Plesk Panel (at Domains > domain name > Mail group title menu > Mail Settings > Switch on greylisting spam protection for all mail accounts under this domain 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.