Don't use webmail / view HTML spam emails
The result is they build up a list of known good email addresses which they use / trade / sell to other spammers = even more spam.
This is largely unavoidable with web based email systems (by their very nature) but with normal email programs (Outlook / Outlook Express etc.) you can turn off viewing as HTML and it will display as plain text.
If you recognise the sender you can usually still view the HTML version but by turning it off by default you are not 'automatically' viewing / previewing the message and therefore not confirming your email address to all the spammers!
To turn off viewing of HTML email in Microsoft Outlook Express:
- Select 'Tools'
- Select 'Options'
- Click the 'Read' tab
- Select 'Read all messages in plain text'
- Click 'Ok'
If you do then receive a HTML formatted email you need to see - select 'View' then 'Message in HTML' or use the keyboard shortcut: Alt-Shift-H