If you are receiving unwanted messages to what is not your email id, you can create filter based on receiving address to delete.

Good to know, thanks. I'm not too knowledgable about Thunderbird settings. Can you explain to me HOW to block messages being sent TO a particular e-mail address (not mine), which messages spill over into my own account?

I did a sample. You may need to fiddle a bit if it isn't want you want. - click tools>message filters - select the account and click 'new' - fill in the options such as in my attached screenshot. It's fairly straightforward. In my example, I am assuming it is already in junk status, but you can change it to be prior to assuming junk status. After a few tries, I think you'll find what works.

Thx very much. I made a couple of modifications to your filter suggestions. I looked up "@ziggo.nl" on the Internet, and I don't think that anything from that domain would be relevant; I've attached an image of my filter. What do you think? I'll give it a try and see how it works. Question: What does it mean "Set Junk Status to --- Not Junk"? Best wishes, S.

My apologies. In responding, I reversed what you wanted. I was suggesting a filter to make NOT junk, but what you want is to make it junk. So, - set the filter to run BEFORE the junk classification - move message to trash- see attached screenshot.