There’s not a lot you can do to stop people (or robots) from sending you junk email. In most cases it is not worth (and not even safe) to use the “unsubscribe” links in spam emails or to reply to request removal. In 99% of cases the reply address is forged anyway. You can unsubscribe from emails and newsletters from reputable companies, you will have to use your own judgment to decide.
Check with your ISP or mail host to see if they have some server-side filtering that you can enable or customize. This will stop the emails from being downloaded to your machine. Be aware however, that if you set the filters too aggressively, you will be blocking some real emails (false positives) and you won’t know about it. See if the ISP also offers a ‘whitelist’ feature, where you can specify senders you know and trust, emails from these addresses will be passed through the filters without blocking.
Once the spam has made it through to your machine, your task is to separate and delete the unwanted mails. Look through the manuals or the Help screens of your mail program to see if you can enable junk mail filters, or for instruction for writing some custom rules to send spam emails to the trash.
Limit the places that your real email address gets given out – particularly on social media sites, online forums, blogs and other public places. However, once your address is out there, the spammers will sell it to each other so you don’t have much control over how your address is spread around and used for spam.
In an extreme case, you may have to abandon your email address and get a new one.
There are some third party programs that can help clean your inbox
Spam Fighter (Commercial, 30 day trial) http://www.spamfighter.com/
Cloudmark Desktop – free and commercial versions (Win only) http://www.cloudmarkdesktop.com/
SpamReader – open source filter for Outlook (Win only) http://www.spam-reader.com/
You can also access your email account through Google mail with Google MailFetcher, which applies an anti-spam filter.
http://mail.google.com/support/bin/answer.py?answer=21288
And there are a variety of services that route your email through another server to test it before downloading.
http://en.wikipedia.org/wiki/Spam_filter
http://en.wikipedia.org/wiki/E-mail_filtering
If you run your own business mail server, or can control the software installed on your host’s mailserver, there are a variety of business solutions
SpamAssassin (open source) http://spamassassin.apache.org/
ASSP (open source) http://sourceforge.net/projects/assp/
Google Business Apps / Postini http://www.google.com/postini/
plus many others
http://www.idswebhosting.com/blog/web-hosting-stuffs/spam-filter-comparison-who-makes-the-best-spam-filter/
http://en.wikipedia.org/wiki/Anti-spam_techniques_%28e-mail%29#Automated_techniques_for_e-mail_administrators
And there are hardware firewall solutions with anti spam and anti virus built in