Well, I use Outlook Express, and it's got a facility called Block Sender (in the menu that opens when you click on Message at the top of the page). I imagine most emaio programs have something similar.

You can use it to block all future messages from a particular sender, and also to remove all previous messages from them, if you wish. It makes getting spam a bit like playing Space Invaders.

And that's what I'd do, if I wanted to stop someone sending undanted messages to me, rather than bothering to ask them to remove me from their mailing list.

And, as it happens, I wouldn't wish to use it on either WYSIWYG or Brendy.