Judy and I both have a program called MailWasher, recommended by a list
member years ago, that allows you to preview all your e-mail before
downloading it. You can designate senders as Friends or Blacklisted.
Blacklisted e-mails get returned to the sender as undeliverable and any
subsequent e-mails from that sender are automatically dumped before they
reach your mailbox. It's very easy to use and has great support. When
I first got an e-mail from Greta, I just Blacklisted her and haven't
heard from her since. See their products at http://www.firetrust.com/
You can get a free trial download.