Because of this, the best spam indicator for me is when the same email has been sent to several of my addresses. Does anyone know of a spam filter that works on this basis??
That depends on how you get your email. If you run (or have control over) your mailserver, then it's easy to do there -- contact me offline if you want more info. I'm not as up to speed on the PC client end of things (as I do my spam filtering on my server
).
It would seem to be trivial for an ISP to filter out spam based on either (a) looking for emails being sent to thousands of their users at once, or (b) looking for emails being sent to dummy 'honeytrap' addresses, or (c) both. There would be a huge market for guaranteed spam-free hosting - why don't they do it???
There would be a risk that bulk email from 'legitimate' sources like Amazon might get killed too, but the honeytrap addresses shouldn't ever receive those ones...
Beacuse you (a) cannot guarantee that any given spam will include the "honeytrap" address and (b) you cannot safely assume that mail to "thousands of their users at once" is spam -- many users may well have singned up to a popular newsletter which they may well all recieve at once.
I am firmly of the view that it should
not be the
recipient (or their ISP) who have to bear the cost of anti-spam measures [well, except as described below.] It should be the
sender's ISP who should be penalised for tolerating spammers as
their users.
There is a way of doing this, but it's not a "quick fix" (which is what most people want
) -- it's very much short term pain for long(er) term gain.
There are a number of "Realtime Blocking Lists" (with different "membership" criteria) which allow ISPs or people running their own servers to refuse to accept incoming mail from servers or whole networks (read ISPs) based on those criteria. This is the most efficient way of blocking mail from the recipient's (or their ISP's) point of view -- no disk space required to store the spam while it's scanned, no additional CPU resources needed to scan it to establish if it's spam, etc.
Of course, the downside is that this will block legitimate email as well (in the short term), but it pushes the cost of dealing with the spam back onto the
spammer's ISP -- it's now they who have their disk clogged up with all the mail that everybody else is refusing to accept -- until
they choose to be less spam friendly and thus get themselves off the Bloking Lists.
Rant over