Blocking certain emails

Question

I get junk mail all the time and i was wondering if i could block specific email addresses (mac os 10.4.3)

Answer 1

Since spammers don't provide a valid sending or return email address and are constantly changing the bogus email address used (much of the same junk that appears to be sent by a different email address are being sent by the same person and computer), this is waste of time and can't be done with any email client anyway.
This can only be done at the incoming mail server level by your ISP or email account provider.
Do you automatically render all HTML received and/or do you provide this email address when making online purchases, for any website access if required or for any other "public" purpose?
Regarding automatically rendering all HTML received, your email address can be logged as a "known good" address by a spammer if the spammer includes any embedded images or objects with HTML that must be rendered from a remote server. If the Mail.app junk filter automatically marks a message as junk, any embedded images or objects will not be rendered when the message is opened but if a junk message is not automatically marked as junk and contains embedded images or objects and it is opened, you can be revealing that your email address is valid to the spammer causing you to receive even more spam. Spammers also sell/trade their lists of "known good" email addresses so it becomes an endless cycle.
Does your ISP or email account provider include a method to forward any spam received to them with long headers shown for the received message? If so, your ISP or email account provider can then determine the computer IP address where the messages originated and block that IP address from being able to send messages to any email address in your ISP's or email account provider's domain.
If you are providing this email address for any online purchases, website access or for any other public purpose where this email address can be harvested by spammers, you need to have a private and public email address. Use the private email address to exchange email with family and friends ONLY. Get a free Hotmail or Yahoo account/address with webmail access only to be used for public purposes.
Once the cat is out of the bag, it is too late so this may require cancelling this email address and getting a new "private" address along with not automatically rendering all HTML received.