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I have failed to find an answer as to why Thunderbird fails to take tally of an incoming e-mail that I mark as 'junk'. Even setting up Mail Filters does not prevent the next arrival from the same source from passing through the filtering and arriving again in my In-Box. Can I prevent this and if so how, or is it the result of the sender's clever machinations to avoid my blocking?

Well it sounds to me like they have evaded your filter. otherwise it would be where your filter placed it. Apparently it is not.

It is a very common misconception that the junk filter does or should take any notice of an email address, other than to check if the sender is in your address book.

The junk filtering uses Bayesian mathematics and serves me exceedingly well. But it has been using my choices of junk and not junk for 10 years, to learn what I think is junk and blend that into the general equation. But then I am understanding of some of the issues.

Machines do not read images. People do. So junk messages with images defeat all but the most expensive junk filters that use OCR to identify the text.

SPAM rarely comes from the same address twice. unsolicited marketing material, or subscribed material does. If it is a condition of membership of a site that you accept their barmy newsletter, simply cease your membership, or unsubscribe. Do not look for software that allows you to break the terms of use of the site. Everything has a cost. Nothing in life it truly free and these sites charge you by sending you mail.

Another total fallacy is that there is a list of words that trigger junk classification If there were to mention Viagra here would see the support email tossed in the trash as junk. Certain words are weighted higher than others.

In the language of spam testing words are refered to a tokens.

Using an email I received from this thread https://support.mozilla.org/en-US/questions/1142101 I can see that the string "want" gets a high value. would you be looking at that sort of detail in the content of an email. I would not. But just as a teacher scores a test the junk filter compared notes and anything with a score over 90 gets tossed into the junk.

Filters Filters are "per account" so if you create a filter on one mail account. It will not apply to others. Likewise filters default to the local folders account. Lots of first time filter authors do not correct that so their filters simply never fire as the account never gets any mail. Have you specified the correct account.

The best reply I can think of is to send you a link to the Junquilla addon which is designed to expose some of the workings of the Junk controls. It describes the scoring system and how you might adjust it to suit your own needs.

The bottom line is that Thunderbird's Junk recognition system pays no attention to senders. In spam these are always spoofed or fake and so unreliable for classification purposes. I am currently running a test where I collate spammers' addresses into an address book and use this to reject messages from known sources. It is proving to be woefully ineffectual. Wildcard matches on specific words in the subject might work better, using filters, but maintaining filters is hard work and you're constantly playing catch up and reacting to trends.

My own issue with Thunderbird is that contrary to what we are told, messages from senders who are already in my Address Book are occasionally classified as Junk and this is not supposed to happen.

Certainly, effective spammers make their product hard to recognise (computationally speaking) by using a large number of common words and thus avoiding simplistic pattern recognition.

http://mesquilla.com/extensions/junquilla http://kb.mozillazine.org/Junk_Mail_Controls

Zenos said

My own issue with Thunderbird is that contrary to what we are told, messages from senders who are already in my Address Book are occasionally classified as Junk and this is not supposed to happen.

Zenos, Are the address books selected in account settings? The default in my experience is no address books are selected until the user selects them.

As it has never been an issue for me, I never bothered to select them. After all my wife was an excellent source of SPAM for a while a couple of years ago. And then I was spamming myself. That junk would have appeared in my inbox if I had white listing selected.

My thanks to Matt and Zenos for their very helpful and interesting replies. Information gratefully taken on board - Junquilla in my sights.