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On Wed, 21 Apr 2010, Julian Hall wrote:
On 21/04/2010 09:30, Gordon Henderson wrote:If you don't have control of the mail server (and by that I really mean root access), then you're limited to filtering, but you also have to accept that you need to copy all the email off the remote server to your local systems, then filter out the spam as you go.
Not if you use Thunderbird's 'Delete from server' filter action as this deletes mail before it even gets to you.
You think so?How does it know that the message on the server is spam? The only way it can know is if it downloads the message headers to see if there are any spam-flags set by the server, or downloads the entire message to see if it's "spammy" then it can flag it as deleted on the server without passing it on to you.
So while you may not see the message in the in-box maintained by Thunderbird, to do that it's had to download the message (thus using up part of your bandwidth allowance) to check for spam, then send the delete command to the server.
The net result is that you have paid for the bandwidth used to copy the email from the server to your PC running TB, for each message whether it's spam or not, and TB has used up your CPU cycles to check the message for spam.
I recently had a customer who was targeted by a spammer for some reason or other (never got to the bottom of it, but on their insistence, and despite my best efforts to persuade them otherwise, they had a wildcard mail-drop email address). They were seeing 15,000 emails a day and trying to download them all to their local PC which had anti-spam software on it. They gave-up after a while because their ADSL line couldn't cope.
So for myself, I've now successfully moved from email client-side filtering to server filtering for my own uses and wished I'd done it years ago. Now, I can use any email client I like (pine/alpine/webmail/mobile phone) and see my email and all my bulk incoming email (spam, automated messages, etc.) is filtered into mailboxes on the server. You can't do this as you need thunderbird to do the filtering for you, so when you access your email from a different system, you don't get the filtering benefit - you have a bulky GUI email client, bulked out more with filtering code and spam detection when that really ought to be on the server where it belongs.
(says the recently procmail converted evangelist ;-) Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html